hooks: macbind - Attach vm nics to specified bridge

This hook support binding specified vNIC identified by its mac address
to custom/other bridge than the currently defined bridge in ovirt.
This hook is also capable of binding a vNIC to a openvswitch bridge.

This hook differs from existing "exnet" hook in 2 points:
 - It is not dependent on a network defined in libvirt. macbind works
 with any existing bridge on the system.
 - It is per VM and not per virtual nic. User have an option to change
 the attachment of one or more virtual nic to different bridges in that
 specific 'vm run', even-though the vnic is permanently attached to a
 different bridge.

Change-Id: I0356dfab224a9082b44aae1c66df050f7456301c
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1091005
Signed-off-by: Humble Chirammal <hchiramm@redhat.com>
Signed-off-by: Amador Pahim <apahim@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/17895
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>