Only explictly create internal bridges (those with no local PIFs) from Xapi_network.attach_internal.
Only explictly create internal bridges (those with no local PIFs)
from Xapi_network.attach_internal.

external bridges are brought up and configured by calling
interface-reconfigure.

Has no impact when using Linux bridging but when vswitch is enabled it
prevents the creation of spurious bridges when attaching a VLAN
network (since there is not supposed to be a separate bridge in that case).

Signed-off-by: Ian Campbell <9be92b3dbbd6611e3e4c9209fb3d04b4919e7cca@citrix.com>

koushikcgit/xcp-rrdd,djs55/xcp-rrdd,djs55/xcp-networkd,djs55/xcp-networkd,simonjbeaumont/xcp-rrdd,sharady/xcp-networkd,johnelse/xcp-rrdd,koushikcgit/xcp-rrdd,djs55/xcp-rrdd,johnelse/xcp-rrdd,robhoes/squeezed,sharady/xcp-networkd,koushikcgit/xcp-networkd,koushikcgit/xcp-networkd,simonjbeaumont/xcp-rrdd,koushikcgit/xcp-rrdd,djs55/squeezed