Add 'modem set-logging' command.

The 'modem set-logging' command replaces 'mm_debug' for setting logging
level in modem managers.

BUG=chromium-os:34360
TEST=Tested 'modem set-logging' with cromo and ModemManager.

Change-Id: I11c68eb36d602f5ff1fd5e06418e824b56d33fb7
Reviewed-on: https://gerrit.chromium.org/gerrit/33114
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Thieu Le <thieule@chromium.org>
2 files changed