Automatic merge from submit-queue (batch tested with PRs 38294, 37009, 36778, 38130, 37835)
Re-use tested ratelimiter
The ratelimiter introduced in #35583 is not working correctly when called from multiple threads
This reverts to the tested ratelimiter we were previously using to unblock 1.5 (automated revert wasn't possible)
Ref #38273
reproducing test case:
```
func TestMultiThreadedBlocking(t *testing.T) {
done := make(chan bool)
// 100 QPS, burst of 100
b := NewBucketWithRate(100, 100)
go func() {
defer close(done)
fmt.Println(time.Now(), "Waiting for 1000 (should block for ~9-10 seconds)")
b.Wait(1000)
fmt.Println(time.Now(), "Got 1000")
}()
// give the request for 1000 plenty of time to take the tokens
time.Sleep(2 * time.Second)
fmt.Println(time.Now(), "Waiting for 1 (should wait until 1000 block is refilled)")
b.Wait(1)
fmt.Println(time.Now(), "Got 1 (should happen right after the wait for 1000 completes)")
<-done
}
$ go test ./pkg/util/ratelimit/ -v -run TestMultiThreadedBlocking
=== RUN TestMultiThreadedBlocking
2016-12-07 12:15:36.222133049 -0500 EST Waiting for 1000 (should block for ~9-10 seconds)
2016-12-07 12:15:38.222797752 -0500 EST Waiting for 1 (should wait until 1000 block is refilled)
2016-12-07 12:15:38.222897951 -0500 EST Got 1 (should happen right after the wait for 1000 completes)
2016-12-07 12:15:45.223125234 -0500 EST Got 1000
```
in contrast, the same test run against juju/ratelimit:
```
go test ./pkg/util/flowcontrol/ -v -run TestMultiThreadedBlocking
=== RUN TestMultiThreadedBlocking
2016-12-07 12:32:56.796077782 -0500 EST Waiting for 1000 (should block for ~9-10 seconds)
2016-12-07 12:32:58.799159059 -0500 EST Waiting for 1 (should wait until 1000 block is refilled)
2016-12-07 12:33:05.801076002 -0500 EST Got 1000
2016-12-07 12:33:05.807510387 -0500 EST Got 1 (should happen right after the wait for 1000 completes)
--- PASS: TestMultiThreadedBlocking (9.01s)
```
440ed2cfa8