lxd/device/bic/bridged: Fixes openvswitch port leak when device is stopped
lxd/device/bic/bridged: Fixes openvswitch port leak when device is stopped

Port was not being detached from bridge on stop causing disconnected ports to accumulate on bridge:

 sudo ovs-vsctl show
 84593e35-9a66-45ba-b647-929e396b3a59
    Bridge lxdbr1
        Port lxdbr1
            Interface lxdbr1
                type: internal
        Port veth1d5cd6a9
            Interface veth1d5cd6a9
                error: "could not open network device veth1d5cd6a9 (No such device)"

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

stgraber/lxd,atxwebs/lxd,mjeanson/lxd,atxwebs/lxd,hallyn/lxd,Skarlso/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,mjeanson/lxd,lxc/lxd,hallyn/lxd,atxwebs/lxd,mjeanson/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,hallyn/lxd,Skarlso/lxd,lxc/lxd,Skarlso/lxd,hallyn/lxd,Skarlso/lxd,lxc/lxd,atxwebs/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd