Add the root path of the services to python path, not services/.

Get rid of the now useless env.get_services_dir

services/presence/sugar-presence-service

@@ -24,11 +24,11 @@ import os
 from sugar import logger
 from sugar import env
 
-sys.path.insert(0, env.get_services_dir())
+sys.path.insert(0, os.path.join(env.get_data_dir(), 'services/presence'))
 
 logger.start('presenceservice')
 
-from presence import PresenceService
+import PresenceService
 
 logging.info('Starting presence service')