bond: Ignore desired MAC when in MAC restricted mode

For active-backup bond with `fail_over_mac: active`, the MAC address of
bond is determined by its bond port, previously we raise error when
this bond in desired state has MAC address defined.

This cause problem when user try to apply the state retrieved by
`nmstatectl show`.

Instead of raising error, this patch just discard desired MAC address
and raise an warning message. If user desired invalid MAC address(not
bond port MAC address), verification stage will fail the apply action.

Unit and integration test cases updated.

Resolves: https://issues.redhat.com/browse/RHEL-106135

Signed-off-by: Gris Ge <fge@redhat.com>