changed the tileout of proxy method calls via zmq to 15s

it was 5s formerly, but if used for database calls for instance, the
database connection itself has a timeout of 15s, so it may be longer
than the initial 5s.

python/soma_workflow/zro.py

@@ -514,7 +514,7 @@ def get_socket(self):
 
     def __call__(self, *args, **kwargs):
         try:
-            timeout = 5000  # ms
+            timeout = 15000  # ms
             logger = logging.getLogger('zro.ObjectServer')
             logger.debug('Execute method: %s.%s(*%s, **%s)'
                          % (self.proxy.classname, self.method, repr(args),