Add test that OS is operation after master fail

Test verifies that openstack is operational
after master node is failed. Scenario:
* Deploy simple nova flat
* verify that deployment is successful
* run ostf
* destroy admin node
* verify openstack

Closes-bug: #1259460
Change-Id: I9e1d1fb2f3c6f642c23a509ac41580e5c53bf952
Merge "Add test that OS is operation after master fail"