Add local service check

After noticed non-root user can list devstack services in plugin's
triggered jobs, fixed past review comment to use preferred `systemctl`
instead of configurable directory existence check.

Added common local service check function to reduce repeated code.

Small code improvements along the way, like sparing second shell
call when podified setup used.

Change-Id: Idbb98765ef2020d674ed00f3b43193d0bed935d2

whitebox_neutron_tempest_plugin/common/utils.py

@@ -51,13 +51,20 @@ def is_regex_in_file(regex, filename, re_flags=0, fail_no_file=True):
     return result
 
 
-def _is_devstack_wsgi():
-    # TODO(rxiao): remove this check when/if API check exists
-    if shell.execute(
+def is_local_service(service_name):
+    """Returns if local service exists"""
+    return bool(
+        shell.execute(
             "systemctl list-unit-files --type service | "
-            "grep devstack@neutron-api", check=False).stdout.strip():
-        return True
-    return False
+            f"grep '{service_name}'",
+            check=False
+        ).stdout.strip())
+
+
+def is_devstack_wsgi():
+    """Returns if wsgi according to neutron api service name when used"""
+    # TODO(rxiao): remove this check when/if API check exists
+    return is_local_service('devstack@neutron-api')
 
 
 def conf_action(

whitebox_neutron_tempest_plugin/tests/scenario/base.py

@@ -56,14 +56,9 @@ ConfigOption = collections.namedtuple(
 
 class BaseTempestWhiteboxTestCase(base.BaseTempestTestCase):
     credentials = ['primary', 'admin']
-    # NOTE(mblue): change devstack check if CI must not use /opt/stack,
-    # currently used commonly for devstack jobs needed by plugin.
     if 'is_devstack' not in locals():
-        is_devstack = bool(shell.execute(
-            'test -d /opt/stack && echo stack',
-            check=False).stdout.strip())
-    if 'is_devstack_wsgi' not in locals():
-        is_devstack_wsgi = local_utils._is_devstack_wsgi()
+        is_devstack = local_utils.is_local_service("devstack@")
+        is_devstack_wsgi = is_devstack and local_utils.is_devstack_wsgi()
 
     @classmethod
     def resource_setup(cls):