Run functional test correctly

legacy-neutronclient-test-dsvm-functional job actually runs
neutronclient.tests.unit because .stestr.conf does not honor
OS_TEST_PATH. This commit fixes .stestr.conf to honor OS_TEST_PATH
specified in tox.ini.

Also fixes the logic of is_extension_enabled() in ClientTestBase
to check whether FWaaS v1 (fwaas) is enabled correctly.
Previously the logic checks a substring of a specified extension,
so 'fwaas' (FWaaS v1) matches 'fwaas_v2' (FWaaS v2),
which leads to a failure of FWaaS v1 CLI tests.

Change-Id: I958ad496b16cca8d03a7b84ebf5f8f031e4248ea

.stestr.conf

@@ -1,3 +1,3 @@
 [DEFAULT]
-test_path=./neutronclient/tests/unit
+test_path=${OS_TEST_PATH:-./neutronclient/tests/unit}
 top_dir=./

neutronclient/tests/functional/base.py

@@ -76,7 +76,5 @@ class ClientTestBase(base.ClientTestBase):
 
     def is_extension_enabled(self, extension_alias):
         extensions = self.parser.listing(self.neutron('ext-list'))
-        for extension in extensions:
-            if extension_alias in extension['alias']:
-                return True
-        return False
+        aliases = [e['alias'] for e in extensions]
+        return extension_alias in aliases