archive/zip, crypto/tls, net/http: Fix print format errors.

All of the errors were located using "go vet ./..." in "src/pkg".

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/6856056

prf_test.go

@@ -51,7 +51,7 @@ func TestKeysFromPreMasterSecret(t *testing.T) {
 
 		masterSecret := masterFromPreMasterSecret(test.version, in, clientRandom, serverRandom)
 		if s := hex.EncodeToString(masterSecret); s != test.masterSecret {
-			t.Errorf("#%d: bad master secret %s, want %s", s, test.masterSecret)
+			t.Errorf("#%d: bad master secret %s, want %s", i, s, test.masterSecret)
 			continue
 		}