spec: F15 still uses cgconfig, RHEL lacks hyperv

Commit ecd8725c dropped attempts to probe the cgconfig service on
new enough Fedora where systemd took over that aspect of the system,
but mistakenly used F14 instead of F15 as the cutoff point.

https://bugzilla.redhat.com/show_bug.cgi?id=741358

Also, RHEL does not include HyperV support yet.

* libvirt.spec.in (with_cgconfig): Check cgconfig service in F15.
(%{?rhel}): Provide default for with_hyperv.

libvirt.spec.in

@@ -97,7 +97,8 @@
 %endif
 
 # RHEL doesn't ship OpenVZ, VBox, UML, PowerHypervisor,
-# VMWare, libxenserver (xenapi), or libxenlight (Xen 4.1 and newer)
+# VMWare, libxenserver (xenapi), libxenlight (Xen 4.1 and newer),
+# or HyperV.
 %if 0%{?rhel}
 %define with_openvz 0
 %define with_vbox 0
@@ -106,6 +107,7 @@
 %define with_vmware 0
 %define with_xenapi 0
 %define with_libxl 0
+%define with_hyperv 0
 %endif
 
 # RHEL-5 has restricted QEMU to x86_64 only and is too old for LXC
@@ -894,9 +896,9 @@ done
 %endif
 
 %if %{with_cgconfig}
-# Starting with Fedora 15, systemd automounts all cgroups, and cgconfig is
+# Starting with Fedora 16, systemd automounts all cgroups, and cgconfig is
 # no longer a necessary service.
-%if 0%{?fedora} <= 14 || 0%{?rhel} <= 6
+%if 0%{?fedora} <= 15 || 0%{?rhel} <= 6
 if [ "$1" -eq "1" ]; then
 /sbin/chkconfig cgconfig on
 fi