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/handler_pod_insecure_test.go

@@ -89,6 +89,8 @@ func TestServeDNSModeInsecure(t *testing.T) {
 			t.Fatalf("Test %d, got nil message and no error for %q", i, r.Question[0].Name)
 		}
 
-		test.SortAndCheck(t, resp, tc)
+		if err := test.SortAndCheck(resp, tc); err != nil {
+			t.Error(err)
+		}
 	}
 }