CA-116420: when creating linux bond, add MAC address after adding bond slaves

This is needed under kernel 3.x, because the kernel now changes the bond
MAC to the MAC of the first slave that is added, which is not always
what we want.

Imported from xcp-networkd.git 0726ee01d071daa0ed8f1011e8bd5e6b05fee47b

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Imported-by: John Else <john.else@citrix.com>