bump bbs
bump bbs

[finishes #121429723]

Submodule src/github.com/cloudfoundry-incubator/bbs 2916727..ec7109d:
  > use local variable instead of overwriting the global EvacuationQuery var
  > formatting
  > wip: getting rid of upsert

Signed-off-by: Danny Cao <5ffc8b7cff3b9f2acb630fd157ff837ced3278ae@us.ibm.com>

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release