shared folders cannot be mounted on OSX

[kgignatyev-inspur]

**Is this a BUG REPORT

Please provide the following details:

Environment:

Minikube version (use minikube version):
minikube version: v0.28.0

• OS (e.g. from /etc/os-release):
  OSX 10.13.6

• VM Driver (e.g. cat ~/.minikube/machines/minikube/config.json | grep DriverName):
  "DriverName": "virtualbox",

• ISO version (e.g. cat ~/.minikube/machines/minikube/config.json | grep -i ISO or minikube ssh cat /etc/VERSION):
  "Boot2DockerURL": "file:///Users/kgignatyev/.minikube/cache/iso/minikube-v0.28.0.iso",

What happened:

Host shared folder is not mounted

What you expected to happen:

Users folder to be mounted

How to reproduce it (as minimally and precisely as possible):

try to reach shared folder from host

Output of minikube logs (if applicable):

Anything else do we need to know:

It looks like virtualbox guest additions installation fails, when I mounted guest additions and tried to install them I got:

./VBoxLinuxAdditions.run
Verifying archive integrity... All good.
Uncompressing VirtualBox 5.2.14 Guest Additions for Linux........
bzip2 not found. Please install: bzip2 tar; and try again.

[dlorenc]

This should be fixed by #2986