Remove "stop modemmanager" in set_celluar_mode

It's better to use "exclusive=['NETWORKING']" in test_list.

BUG=chrome-os-partner:22433
TEST=Manual

Change-Id: I1aa3680ae1d50e5a3d037a8ec36c144943c1a766
Reviewed-on: https://chromium-review.googlesource.com/168004
Reviewed-by: Bowgo Tsai <bowgotsai@chromium.org>
Commit-Queue: Bowgo Tsai <bowgotsai@chromium.org>
Tested-by: Bowgo Tsai <bowgotsai@chromium.org>
1 file changed