Stop importing testing in the main binary (#2479)

* Stop importing testing in the main binary

Stop importing "testing" into the main binary:

* test/helpers.go imported it; remote that and change function signature
* update all tests that use this

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

* Drop import testing from metrics plugin

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

* more fiddling

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

plugin/kubernetes/reverse_test.go

@@ -200,6 +200,8 @@ func TestReverse(t *testing.T) {
 		if resp == nil {
 			t.Fatalf("Test %d: got nil message and no error for: %s %d", i, r.Question[0].Name, r.Question[0].Qtype)
 		}
-		test.SortAndCheck(t, resp, tc)
+		if err := test.SortAndCheck(resp, tc); err != nil {
+			t.Error(err)
+		}
 	}
 }