build-unit-test-docker: convert to Python

Do a near identical conversion from bash to Python for the script which
builds the unit-test docker containers.  I plan to do additional
enhancements to build the sub-containers in parallel, so I needed to
first do this conversion to Python in order to make that implementation
sane.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I6df6f294b41f3a01f95fbe23a6dcd1ea21a315a9
4 files changed