Seperating supervdsm log to supervdsm.log file

Supervdsm as root process can change the logfile ownership
to root when creating the file. Manual deletion of vdsm.log can cause
this scenario.

Change-Id: I2e5fb4a2cd5421671f942120b6718c1bb20b9e60
Bug-Id: https://bugzilla.redhat.com/show_bug.cgi?id=912308
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: https://gerrit.eng.lab.tlv.redhat.com/7190
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/13964