Update RecordTimer.py

EMC: [emcRC] recEvent exception:
'RecordTimerEntry' object has no attribute 'MountPath'
Unexpected error: <type 'exceptions.AttributeError'>
Traceback (most recent call last):
  File "/usr/lib/enigma2/python/Plugins/Extensions/EnhancedMovieCenter/RecordingsControl.py", line 107, in recEvent
  File "/usr/lib/enigma2/python/RecordTimer.py", line 193, in calculateFilename
    self.Filename = Directories.getRecordingFilename(filename, self.MountPath)
AttributeError: 'RecordTimerEntry' object has no attribute 'MountPath'