spec: Fix polkit dep on F23

As of fedora polkit-0.113-2, polkit-devel only pulls in polkit-libs, not
full polkit, but we need the latter for pkcheck otherwise our configure
test fails.

libvirt.spec.in

@@ -531,6 +531,8 @@ BuildRequires: cyrus-sasl-devel
 %endif
 %if %{with_polkit}
     %if 0%{?fedora} >= 20 || 0%{?rhel} >= 7
+# F22 polkit-devel doesn't pull in polkit anymore, which we need for pkcheck
+BuildRequires: polkit >= 0.112
 BuildRequires: polkit-devel >= 0.112
     %else
         %if 0%{?fedora} || 0%{?rhel} >= 6