Revert "port-mbim: use the mbim-proxy by default"

This reverts commit a22681ba99f8249a5d516dca773b125c0bdf0912.

Temporarily disable mbim-proxy until we can run ModemManager and
mbim-proxy under a non-root user.

BUG=chromium:421293
TEST=`FEATURES=test emerge-$BOARD modemmanager-next`
TEST=Run network3g tests on a DUT with a MBIM modem.

Change-Id: I253572bf3c1a0c0d57fb66338c8e37399cd6c974
1 file changed