proftpd/test/utils: fix check for AF_UNIX path too long

supervisord creates a socket with pid in the name, so we have to account
for the space of pid.

Because it's not so easy to know the max size of pids, we just assume 7
places.

software/proftpd/test/utils.py

@@ -83,8 +83,11 @@ class SlapOSInstanceTestCase(unittest.TestCase):
     # AF_UNIX path too long This `working_directory` should not be too deep.
     # Socket path is 108 char max on linux
     # https://github.com/torvalds/linux/blob/3848ec5/net/unix/af_unix.c#L234-L238
-    if len(working_directory + '/inst/supervisord.socket') > 108:
-      raise RuntimeError('working directory too deep, try setting SLAPOS_TEST_WORKING_DIR')
+    # Supervisord socket name contains the pid number, which is why we add
+    # .xxxxxxx in this check.
+    if len(working_directory + '/inst/supervisord.socket.xxxxxxx') > 108:
+      raise RuntimeError('working directory ( {} ) is too deep, try setting '
+              'SLAPOS_TEST_WORKING_DIR'.format(working_directory))
 
     if not os.path.exists(working_directory):
       os.mkdir(working_directory)