spec: bump libvirt version for el6

The new libvirt version includes several bugfixes and enhancements to
increase the reliability and the stability.

Highlights:

- BZ#915347 cannot resume a suspended vm
- BZ#915354 cannot run a vm with several snapshots
- BZ#922095 libvirtd memory leak

Change-Id: I5a9b8f97374938c39f694eb52ecdac6c494b4384
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/13163
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>