Add unittest for e5071c_scpi module.

Rename the unittest from
/src/third_party/autotest/files/client/cros/rf/agilent_scpi_unittest.py
to e5071c_scpi_unittest.py.
Correct the import module path and change the code style with factory.
In addition, fixed a lint error and change the exception type from Error
to ValueError as it changes on e5017c_scpi.py

BUG=chrome-os-partner:20240
TEST=make lint; make test;
and make sure the unittest is executed.

Change-Id: Iab7906f5dd98546a233a08ebaa5c9e142d7632dc
Reviewed-on: https://gerrit.chromium.org/gerrit/61549
Reviewed-by: Jon Salz <jsalz@chromium.org>
Commit-Queue: Chun-Ta Lin <itspeter@google.com>
Tested-by: Chun-Ta Lin <itspeter@google.com>
2 files changed