Do not reference qemu hook on RHEL 6 in spec file

The previous patch skips the qemu hook installation on RHEL 6,
but still references it in the %files section.

This fixes that.

Change-Id: Ic167e5651960519206d9b8cb3a933a2e238d4321
Related-To: https://bugzilla.redhat.com/show_bug.cgi?id=1138340
Signed-off-by: Martin Sivak <mars@montik.net>
Reviewed-on: http://gerrit.ovirt.org/33061
Tested-by: Martin Sivák <msivak@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>