sos: engine: add jboss stack trace

added jbosstrace option, enabled by default, to engine
sos plugin.
The new option send a SIGQUIT signal to the JBoss
process launched by ovirt-engine, causing a dump of
the stack trace to /var/log/ovirt-engine/console.log.

Other JBoss instances will not receive that signal.

Change-Id: Id049f1cc7f322995a8692562a3f7aebddc7cc04d
Bug-Url: https://bugzilla.redhat.com/989484
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>