[milo] {buildbucket,buildbot,swarming,logdog} -> backends/*.

milo/appengine/backends/buildbot/master_test.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package buildbot
 
 import (
         "context"
         "testing"
 
@@ skipping 21 matching lines @@
                         Builders: map[string]*buildbotBuilder{"fake": {}},
                 }, true), ShouldBeNil)
 
                 Convey(`GetAllBuilders()`, func() {
                         cs, err := GetAllBuilders(c)
                         So(err, ShouldBeNil)
                         So(len(cs.BuilderGroups), ShouldEqual, 1)
                 })
         })
 }