      misc/dashboard/app: fix build failure notifications
      misc/dashboard/app: fix build failure notifications

The datastore.Query methods once mutated the Query value, but now they return
a derivative query, so the Hash= and ParentHash= filters were not being
applied.

R=golang-dev, bradfitz, dsymonds
CC=golang-dev
http://codereview.appspot.com/6300058

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang