Description of problem:
when perform stop-rockmongo-1.1 again, it will prompt "Node execution failure (invalid exit code from node)."

Version-Release number of selected component (if applicable):
rhc-broker-0.84.37-1.el6_2.noarch

How reproducible:
always

Steps to Reproduce:
1. Embed mongodb to existing app
#rhc-ctl-app -l bzhao47 -a wsgitest -e add-mongodb-2.0

2. then embed rockmongo  to this app
#rhc-ctl-app -l bzhao47 -a wsgitest -e add-rockmongo-1.1

3. then stop rockmongo , then check this web interface .
#rhc-ctl-app -l bzhao47 -a wsgitest -e stop-rockmongo-1.1

5. stop this rockmongo again
#rhc-ctl-app -l bzhao47 -a wsgitest -e stop-rockmongo-1.1


Notes: test all support kinds of app, like php, wsgi, rack, perl and jbossas. they have the same issue.
  
Actual results:
output "Node execution failure (invalid exit code from node)."

Expected results:
it should return rockmongo has stopped or others info, such as: result success

Additional info:
# rhc-ctl-app -a wsgitest -predhat -e stop-rockmongo-1.1 -d
Contacting https://ec2-107-21-79-175.compute-1.amazonaws.com
Problem reported from server. Response code was 500.

DEBUG:
Cartridge return code: 1

Exit Code: 1
broker_c: namespacerhloginsshapp_uuiddebugaltercartridgecart_typeactionapp_nameapi
api_c: placeholder
API version:    1.1.1
Broker version: 1.1.1

RESULT:
Node execution failure (invalid exit code from node).  If the problem persists please contact Red Hat support.