Speed up testing (#4239)

* Speed up testing

* make notification run in the background, this recudes the test_readme
time from 18s to 0.10s
* reduce time for zone reload

* TestServeDNSConcurrent remove entirely. This took a whopping 58s for
  ... ? A few minutes staring didn't reveal wth it is actually testing.
  Making values smaller revealed race conditions in the tests. Remove
  entirely.

* Move many interval values to variables so we can reset them to short
  values for the tests.

* test_large_axfr: make the zone smaller. The number used 64K has no
  rational, make it 64/10 to speed up.
* TestProxyThreeWay: use client with shorter timeout

A few random tidbits in other tests.

Total time saved: 177s (almost 3m) - which makes it worthwhile again to
run the test locally:

this branch:

~~~
ok  	github.com/coredns/coredns/test	10.437s
cd plugin; time go t ./...
5,51s user 7,51s system 11,15s elapsed 744%CPU (
~~~

master:

~~~
ok  	github.com/coredns/coredns/test	35.252s
cd plugin; time go t ./...
157,64s user 15,39s system 50,05s elapsed 345%CPU ()
~~~
tests/ -25s
plugins/ -40s

This brings the total on 20s, and another 10s can be saved by fixing
dnstapio. Moving this to 5s would be even better, but 10s is also nice.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Also 0.01

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/file/setup.go

@@ -28,9 +28,11 @@ func setup(c *caddy.Controller) error {
 			return nil
 		}
 		f.transfer = t.(*transfer.Transfer) // if found this must be OK.
-		for _, n := range zones.Names {
-			f.transfer.Notify(n)
-		}
+		go func() {
+			for _, n := range zones.Names {
+				f.transfer.Notify(n)
+			}
+		}()
 		return nil
 	})
 
@@ -39,9 +41,11 @@ func setup(c *caddy.Controller) error {
 		if t == nil {
 			return nil
 		}
-		for _, n := range zones.Names {
-			f.transfer.Notify(n)
-		}
+		go func() {
+			for _, n := range zones.Names {
+				f.transfer.Notify(n)
+			}
+		}()
 		return nil
 	})