`test` can now takes several job names

Make the test command to accept several job names. This is exactly like
the change I have made for `update` in 4f5cfb1 (and fixed in fc86fbe).

Change-Id: I68d634b29e4a8ff16818ddeb6f90c7ff072c93a5
Reviewed-on: https://review.openstack.org/26838
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins