Fixed ms users list for tests.

tester.py

@@ -165,7 +165,7 @@ class Tester():
         # Get MS instances
         ms_users = list()
         for user in os.listdir('/home'):
-            if os.path.exists('/home/%s/msinstance' % user) and user == msuser:
+            if os.path.exists('/home/%s/msinstance' % user) and (not msuser or user == msuser):
                 ms_users.append(user)
         # Get MediaServer tests
         if ms_users: