tests: use Errorf instead of Fatal
tests: use Errorf instead of Fatal

http://golang.org/pkg/testing/#B.Fatal
Fatal is going to call FailNow which doesn't work when
called inside a goroutine. Error will call Fail which will
still mark the test as fail.

Change-Id: Ie3fca597fedacb54cf1c58fa77985f2968cef5a6

jchris/indexing,jchris/indexing,jchris/indexing,jchris/indexing