Make query for ssh timeout bug 1298472 more general

This same ssh timeout failure is showing up in at least four different
scenario tests that try to ssh to an instance, so make the query more
general since given the state of the gate right now (terrible), the
underlying root issue is probably the same.

Related-Bug: #1298472

Change-Id: I76a2bf477cad10639f5ec5676d16490a5e687746