Release xenopsd.0.9.39

Signed-off-by: David Scott <dave.scott@citrix.com>
xenopsd.0.9.39: make libvirt a depopt

Unfortunately the version available on travis is too old, let's
make it optional (and hope the pull request builder skips it)

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #28 from djs55/xenopsd.0.9.39

Release xenopsd.0.9.39