Make the combo lock differentiate between users

On the Mark-1 the locking would fail since the first time the lock is
accessed the process is run under root (script checking the enclosure
version). This caused the locking to fail since the normal mycroft
processes got an access error (lock-file owned by root)

This change creates lock-files with a user extension and thus working
around this issue. This leaves a possibility for collisions when
multiple users are running a mycroft process but this VERY rare.

mycroft/util/combo_lock.py

@@ -1,11 +1,18 @@
 from threading import Lock
 from fasteners.process_lock import InterProcessLock
+from getpass import getuser
 
 
 class ComboLock():
-    """ A combined process and thread lock. """
+    """ A combined process and thread lock.
+
+    Arguments:
+        path (str): path to the lockfile for the lock
+    """
     def __init__(self, path):
-        self.plock = InterProcessLock(path)
+        # Append the current username to the path to get separate lock files
+        # for separate users
+        self.plock = InterProcessLock('{}.{}'.format(path, getuser()))
         self.tlock = Lock()
 
     def acquire(self, blocking=True):