Fix unit tests

Due to a recent change in fm-api's directory structure, unit tests would
fail since the virtualenv would not be able to find fm-api/setup.py.
Adjust the tox.ini to point to the correct directory. Tested locally
by running tox.ini.

Depends-On: https://review.opendev.org/c/starlingx/fault/+/806046

Story: 2009101
Task: 43091

Signed-off-by: Charles Short <charles.short@windriver.com>
Change-Id: I6e09735bca06a5c9f0868b58ae7de344299ef570

tox.ini

@@ -92,7 +92,7 @@ commands =
 basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
        -e{[tox]stxdir}/config/tsconfig/tsconfig
-       -e{[tox]stxdir}/fault/fm-api
+       -e{[tox]stxdir}/fault/fm-api/source
        -e{[tox]stxdir}/config/sysinv/sysinv/sysinv
        -e{[tox]stxdir}/config/sysinv/cgts-client/cgts-client
        docutils