There's no need to open ports on non-primary interfaces if ICE is not in
use as these ports will not be used or seen by anyone.
This mostly obsoletes the `save-interface-ports` config option, with the
exception of ICE advertised by the offerer. We currently have no option
to reject ICE from the offerer during the offer phase, so ports would
always be opened on that side.
Relevant to #1164 and 001abe5
Change-Id: I43df70bc0ec49b81f63aec97c776e48617b2acfd