Renaming /etc/sysctl.d/vdsm to /etc/sysctl.d/vdsm.conf

Fixing Bug #740887 it has been added the file /etc/sysctl.d/vdsm which
works fine on RHEL and CentOS but it's not read on Fedora because
it should be /etc/sysctl.d/vdsm.conf ( see sysctl --system output )

Change-Id: I4ac929db854d7a5f9bd96d144e8ef36070f74126
Bug-Url: https://bugzilla.redhat.com/1029368
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21160
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>