Remove skip from test_invalid_host_for_migration().

This commit removes the skip related to a bug, it was fixed as
part of grizzly-3, so we no longer to to skip the test because
of the bug.

Change-Id: I3ee2dab1e92732ad7a9fe5319b35524d7c2aff75
Merge "Remove skip from test_invalid_host_for_migration()."