Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Abhijit Hiremagalur:
     Temporarily disable specs, they are not reliable on mysql ( Travis created: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/22314036 )
     Work around pg vs mysql inconsistency ( Travis Failed: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/22309633 )
     Revert to using the app guid as the event guid after a purge ( Travis Failed: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/22308694 )

Signed-off-by: Kai Zhang <kaizhang@cn.ibm.com>