NEWS: mention the fix for local address use
interfaces: default to use of a local administered MAC address for bonds

Since in the default configuration, some swicthes (Cisco on IOS 15.x)
will complain about MAC addresses flapping when using `configure system
bond-slave-src-mac-type fixed`, and some other switches (still Cisco)
will complain when using `configure system bond-slave-src-mac-type
fixed`, we change the default to `local`. This is not the safest option
but the probability of having a collision is quite low.

Usually, locally administered addresses are used for VM but they are
taken from a known prefix and we are unlikely to have a collision with
this prefix. On VM, we will fallback to a fixed address but hopefully,
the switch will be a virtual one which won't have a problem with the
fixed address.