Switch TM_LOG_DIR to a writable directory

The earlier PR #5184 switched the default TM_LOG_DIR from `logs` to
`/home/appuser` which is not present in circleCI. Switched it out for
/tmp/logs to make tests work.

.circleci/config.yml

@@ -89,8 +89,10 @@ jobs:
       - run: pdm config --global python.use_venv False
       - run: pdm export --prod --without-hashes > requirements.txt
       - run: pip install -r requirements.txt
+      - run: mkdir --mode 766 -p /tmp/logs
       - run: mkdir ${CIRCLE_WORKING_DIRECTORY}/tests/backend/results
       - run: find ./tests/backend -name "test*.py" -exec chmod -x {} \;
+      - run: echo "export TM_LOG_DIR=/tmp/logs" >> $BASH_ENV
       - run:
           name: Run backend functional tests
           command: |