Update and expand machine_manager_unittest.

Expand machine_manager_unittest.py to test all functions in
machine_manager.py.  Modify MachineManager class to optionally take a
command_executer and logger as arguments; also to make command executer
and logger class member attributes (rather than external objects), to
simplify testing.

BUG=None
TEST=Ran unittest to make sure it works; ran all the other unittests; ran
several 'real' crosperf  runs to verify that the changes didn't break
crosperf.

Change-Id: I29798457cb1f7572cb339722b572b9d95b21b989
Reviewed-on: https://chrome-internal-review.googlesource.com/165256
Reviewed-by: Yunlian Jiang <yunlian@google.com>
Commit-Queue: Caroline Tice <cmtice@google.com>
Tested-by: Caroline Tice <cmtice@google.com>
3 files changed