update indigo

Reviewer: trivial

* submodules/indigo 4ce611c...88cdd3a (3):
 > Merge into master from pull request #98: OFConnectionManager: fix
disconnection of listen connections
(https://github.com/floodlight/indigo/pull/98)
 > Merge into master from pull request #99: add role to debug's
(https://github.com/floodlight/indigo/pull/99)
 > Merge into master from pull request #97: prepare ofaux for switchlight
integration (https://github.com/floodlight/indigo/pull/97)