vdsm now prints when a SIGTERM or SIGUSR1 is handled.

Change-Id: I2285a1e4af10bfa40b7e8f1d6a1dba4fd1f7a48c
Signed-off-by: Assaf Muller <amuller@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/14434
Reviewed-by: Dan Kenigsberg <danken@redhat.com>