ovs: allow changing mac address of bridges and interfaces

Allow changing the cloned MAC address for OVS bridges and
interfaces. The MAC address set on the bridge is propagated by ovs to
the local interface (the one with the same name as the bridge), while
all other internal interfaces use the address defined in the interface


(cherry picked from commit 101e65d2)
(cherry picked from commit b366234a)
(cherry picked from commit 5a4a5f63)
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