test_attacker_baremetal: don't run local commands

test_attacker_baremetal: don't run local commands

these tests were failing to mock subprocess.check_output
and thus were trying to run sudo commands on the local
system.

This is dangerous.  Add the subprocess mock.

Also mock the LOG object so we don't print
bogus Runtime error tracebacks in the unittest logs
when we test assertRaises()

Change-Id: I01535f9952fbd95ce2f5972b641c51ff836e7e8c
Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>