tests: print info about failed tests

It's a bit frustrating to run a test normally (e.g. during development),
see a failure, and then have to re-run it with DEBUG=1 to see what
actually failed.  This tiny patch prints out the command line of the
test that just failed, even if DEBUG=0 (in fact only if DEBUG=0 since
otherwise it would be redundant).

Change-Id: Icffa096d0bcc6f35176f0e47d9d1bc538698ca2c
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/7537
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>