Make zookeeper collector py26 compatible and bugfixes

[oozie]

The present zookeeper collector assumes python2.7. In addition to that, this change fixes

• wrong assumptions made about exceptions being returned from subprocess,
• supplying incorrect localhost address for opening socket.

BEFORE:

[root@oozie tcollector]# PYTHONPATH=. ./collectors/0/zookeeper.py 
Traceback (most recent call last):
  File "./collectors/0/zookeeper.py", line 140, in <module>
    sys.exit(main())    
  File "./collectors/0/zookeeper.py", line 101, in main
    instances = scan_zk_instances()
  File "./collectors/0/zookeeper.py", line 50, in scan_zk_instances
    listen_sock = subprocess.check_output(["netstat", "-lnpt"], stderr=subprocess.PIPE)
AttributeError: 'module' object has no attribute 'check_output'

AFTER:

[root@oozie tcollector]# PYTHONPATH=. ./collectors/0/zookeeper.py 
timed out
zookeeper.zk_avg_latency 1442708347 0 port=2181
zookeeper.zk_max_latency 1442708347 13 port=2181
zookeeper.zk_min_latency 1442708347 0 port=2181
zookeeper.zk_packets_received 1442708347 374 port=2181
zookeeper.zk_packets_sent 1442708347 373 port=2181
zookeeper.zk_num_alive_connections 1442708347 2 port=2181
zookeeper.zk_outstanding_requests 1442708347 0 port=2181
zookeeper.zk_approximate_data_size 1442708347 1217 port=2181
zookeeper.zk_open_file_descriptor_count 1442708347 23 port=2181

[vasiliyk]

Merged upstream with commit 38a2b34. Thank you for contributing.