Merge pull request #392 from sequenceiq/ambari17

Integration with Ambari 1.7
CLOUD-306 fixed user management of Ambari
Merge pull request #393 from sequenceiq/user

CLOUD-306 fixed user management of Ambari
CLOUD-306 fixed polling in zones
CLOUD-306 fixed exception handling
CLOUD-306 fixed error message
CLOUD-306 fixed opertaion analyze
CLOUD-306 fixed nullpointer check
CLOUD-306 fixed variable name
Merge pull request #394 from sequenceiq/pollfix

CLOUD-306 fixed polling in zones
CLOUD-304 dummy poller exit
CLOUD-304 fixed pollers
CLOUD-304 pollers with exit criteria
CLOUD-304 fixed polling logics