Run grpc interceptor separately.

tox.ini

@@ -22,12 +22,17 @@ commands =
     python -m pytest {posargs} -n auto \
         {toxinidir}/tests \
         --ignore={toxinidir}/tests/kafka \
-        --ignore={toxinidir}/tests/parallel
+        --ignore={toxinidir}/tests/parallel \
+        --ignore={toxinidir}/tests/grpc/test_interceptor.py
     # kafka and parallel tests are failing for macos when running in parallel
     # with the entire test suite. So, we run them separately.
+    # Also, we run the grpc interceptor test separately because
+    # other tests will interfere with the metrics counter when
+    # running in parallel.
     python -m pytest {posargs} \
         {toxinidir}/tests/kafka \
-        {toxinidir}/tests/parallel
+        {toxinidir}/tests/parallel \
+        {toxinidir}/tests/grpc/test_interceptor.py
 set_env =
     GITHUB_SERVER_URL = {env:GITHUB_SERVER_URL:https\://github.com}
     GITHUB_REPOSITORY = {env:GITHUB_REPOSITORY:SeldonIO/MLServer}