Remove expected failure in OSTF for rollback test

In the test for rollback after failed upgrade we expected
that one health check fails, but currently an environment
has storage nodes, so all checks should pass.

Change-Id: Id8af04ea3875c99914e0d3bf8bf1084a4335120e
Closes-bug: #1396134
Merge "Remove expected failure in OSTF for rollback test"