Update common_adapter.py

add: shell=True for Command run

I want to use arguments for status_cmd, but they are not accepted if shell=True is not set.
An example is as follows:
_q_commands_override:
    submit_cmd: qsub
    status_cmd: qstat -q particular_queue.q

fireworks/user_objects/queue_adapters/common_adapter.py

@@ -249,7 +249,7 @@ def get_njobs_in_queue(self, username=None):
 
         # run qstat
         qstat = Command(self._get_status_cmd(username))
-        p = qstat.run(timeout=self.timeout)
+        p = qstat.run(timeout=self.timeout, shell=True)
 
         # parse the result
         if p[0] == 0: