log: Remove metadata.log

This log exists only in the spec file and logger.conf.
Removing because not used by VDSM.

Change-Id: I56537d2112b8a3e27a65984afc918afd5aa2e96c
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29205
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Tested-by: Yaniv Bronhaim <ybronhei@redhat.com>