schema: bridges was added to VdsmCapabilities

In 1fa30a, Dan added a new field 'bridges' to VdsmCapabilities but did not
update the schema to reflect it.  At the moment we are not checking for
extraneous fields in our types so I just caught it now by chance.

Change-Id: Ib12a7d89c71e6946d12b1a4cb580be1458c280eb
Signed-off-by: Adam Litke <agl@us.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/11396
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>