Move single-request-reopen into OS specific scripts

[rjocoleman]

related to #171

@juliandunn I've completed this move/change.

I established that Fedora 19 and 20 show the same issue under virtualbox.

1. I removed the line from packer/scripts/centos/ks.cfg
2. Added discrete fix-slow-dns.sh scripts for Fedora and Centos/RHEL. These are at the start of post-install script execution incase any later post-install scripts download things so they'll benefit from the fix.
3. Limited the execution of this post-install script to virtualbox only.
4. I moved the Centos into /etc/sysconfig/network, this is used when resolv.conf is generated when dhclient runs. resolv.conf can be overwritten and the change lost otherwise.
5. Fedora uses NetworkManager to generate resolv.conf, added a script to hook into that to add the required line to resolv.conf
6. Fedora 19 has a known bug with the install media version of NetworkManager that prevents dispatchers (the hook I'm using) from running so on F19 updated NM to mitigate this.
7. I built new boxes with the changes applied and verified that they were showing the desired behaviour, as below.

In short this should apply only the the effected operating systems and persist past network changes/reboots.

How to reproduce:

To reproduce this issue I set up a basic Vagrant test: https://gist.github.com/rjocoleman/9161682

Bad:

[default] Running: inline script
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0     26      0  0:00:08  0:00:08 --:--:--    47
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0     34      0  0:00:06  0:00:06 --:--:--    57
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0     34      0  0:00:06  0:00:06 --:--:--    58
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0     33      0  0:00:06  0:00:06 --:--:--    54
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0     34      0  0:00:06  0:00:06 --:--:--    58

Fixed

[default] Running: inline script
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0    323      0 --:--:-- --:--:-- --:--:--   323
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0    305      0 --:--:-- --:--:-- --:--:--   305
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0    289      0 --:--:-- --:--:-- --:--:--   289
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0    274      0 --:--:-- --:--:-- --:--:--   274
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   220  100   220    0     0    326      0 --:--:-- --:--:-- --:--:--   326

[juliandunn]

How often will this run? Is the generation of /etc/resolv.conf by NM convergent? My only concern is that if the user restarts NM then this line will be echoed to resolv.conf each time.

[rjocoleman]

/etc/resolv.conf is made from scratch each time. So we don't need any handling of existing values - it's also why we can't just edit /etc/resolv.conf

$ vagrant ssh -- cat /etc/resolv.conf
# Generated by NetworkManager
domain hq.rjoc.me
search hq.rjoc.me
nameserver 10.0.2.3
options single-request-reopen
$ vagrant halt
... snip ...
$ vagrant up --provider virtualbox
... snip ...
$ vagrant ssh -- cat /etc/resolv.conf
# Generated by NetworkManager
domain hq.rjoc.me
search hq.rjoc.me
nameserver 10.0.2.3
options single-request-reopen
$ vagrant ssh -- sudo service NetworkManager restart
Redirecting to /bin/systemctl restart  NetworkManager.service
$ vagrant ssh -- cat /etc/resolv.conf
# Generated by NetworkManager
domain hq.rjoc.me
search hq.rjoc.me
nameserver 10.0.2.3
options single-request-reopen

[juliandunn]

Ok, LGTM

[juliandunn]

Merged in e236d14