Enable loop device in brilloemulator.

update_engine_unittests needs it.

Test: `ls /dev/loop-control` in brilloemulator-arm
Test: ./site_utils/test_droid.py -s emulator-5554 brillo_WhitelistedGtests
Bug: 28319454

Change-Id: I2d79fa765ded58cde7e8fe19e6e5e3d946952007
1 file changed