Allow tests from plugins

Allow refstack-client run also tests from tempest plugins
by not filtering out all tests whoose names don't start
with tempest.

Change-Id: Ic880967287f7cf7064d2440fde2c35c781477873

refstack_client/list_parser.py

@@ -83,7 +83,7 @@ class TestListParser(object):
         """
         test_mappings = {}
         for testcase in test_list:
-            if testcase.startswith("tempest"):
+            if testcase != "":
                 # Search for any strings like '[smoke, gate]' in the test ID.
                 match = re.search(r'(\[.*\])', testcase)