spec: silence warnings when installing in F16

https://bugzilla.redhat.com/show_bug.cgi?id=738725 documents that
'yum install libvirt' in Fedora 16 is rather noisy.  This fixes
the problems.

* libvirt.spec.in (%post client): Silence chkconfig warning about
SysV services.
(%post) [with_cgconfig]: Drop for Fedora 15 and newer, where
systemd does this automatically.

libvirt.spec.in

@@ -894,10 +894,14 @@ done
 %endif
 
 %if %{with_cgconfig}
+# Starting with Fedora 15, systemd automounts all cgroups, and cgconfig is
+# no longer a necessary service.
+%if 0%{?fedora} <= 14 || 0%{?rhel} <= 6
 if [ "$1" -eq "1" ]; then
 /sbin/chkconfig cgconfig on
 fi
 %endif
+%endif
 
 /sbin/chkconfig --add libvirtd
 if [ "$1" -ge "1" ]; then
@@ -926,7 +930,8 @@ fi
 /sbin/chkconfig --add libvirt-guests
 if [ $1 -ge 1 ]; then
     level=$(/sbin/runlevel | /bin/cut -d ' ' -f 2)
-    if /sbin/chkconfig --list libvirt-guests | /bin/grep -q $level:on ; then
+    if /sbin/chkconfig --list libvirt-guests 2>/dev/null \
+        | /bin/grep -q $level:on ; then
         # this doesn't do anything but allowing for libvirt-guests to be
         # stopped on the first shutdown
         /sbin/service libvirt-guests start > /dev/null 2>&1 || true