vdsm-tool: Add logging configuration.

Added the following flags:
-l/--logfile
-v/vv/vvv/--v/vv/vvverbose
-a/--append

These flags allow specifying where to put the log, how verbose should it
be, and should it truncate the log file before writing.

Change-Id: Ia495743f6e869f65843404e4d4c25c146ff14b43
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29421
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>