labs: move network-api IP address

Eth3 is used for a bridge and should therefore not have an IP address.
With the network-api address remaining on eth3, we can't talk to
controller-api.

This patch moves the IP address to the switch-internal network device
of the bridge, br-ex.

Change-Id: I2a52844a160fe7ccd95e8d1aa16eb2d451dd605f
Merge "labs: move network-api IP address"