RequestContext initialization failed in cinder.

RequestContext initialization failed in cinder because of the following
error:
"TypeError: 'in <string>' requires string as left operand, not NoneType"

It must traverses in tuple not in string when find the "compute"
service_catalog.

Change-Id: I46f4bbd0ffb9d1db8bdcb0254ca95551fea08baf
Closes-Bug: #1248434
Merge "RequestContext initialization failed in cinder."