Check for 'Generated' in SSH key comment

This test fails for https://review.openstack.org/76904 (replace spaces with
dashes in Nova generated SSH key comments) and thus prevents 76904 from
merging. This change simply checks for 'Generated' in the SSH key comment
instead of 'Generated by' which contains a problematic space.

Related-Bug: #1297685
Change-Id: I3adf4e8fa4de3bd7ad7773b345d80e671442ade6
Merge "Check for 'Generated' in SSH key comment"