Make test_tagged_attachment wait for SSHABLE

This test is failing very often, make it wait for the server being
started, this has helped for a lot of other volume related tests, too.

Signed-off-by: Dr. Jens Harbott <harbott@osism.tech>
Change-Id: Ic2b162b0cd4db04dd0f6c47de815e72888d04998
1 file changed