all: use time.Time.Equal instead of == in some tests

(Found by making time.Time uncomparable and rerunning std tests
locally.)

Change-Id: I4fa6fb0ba7334965362387e2f6541c17a27ac3aa
Reviewed-on: https://go-review.googlesource.com/42616
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/go_test.go

@@ -3090,7 +3090,7 @@ func TestGoTestRaceInstallCgo(t *testing.T) {
 	tg.run("test", "-race", "-i", "runtime/race")
 	new, err := os.Stat(cgo)
 	tg.must(err)
-	if new.ModTime() != old.ModTime() {
+	if !new.ModTime().Equal(old.ModTime()) {
 		t.Fatalf("go test -i runtime/race reinstalled cmd/cgo")
 	}
 }

src/net/dial_test.go

@@ -529,7 +529,7 @@ func TestDialerPartialDeadline(t *testing.T) {
 		if err != tt.expectErr {
 			t.Errorf("#%d: got %v; want %v", i, err, tt.expectErr)
 		}
-		if deadline != tt.expectDeadline {
+		if !deadline.Equal(tt.expectDeadline) {
 			t.Errorf("#%d: got %v; want %v", i, deadline, tt.expectDeadline)
 		}
 	}

src/net/dnsclient_unix_test.go

@@ -784,7 +784,7 @@ func TestRetryTimeout(t *testing.T) {
 			return nil, poll.ErrTimeout
 		}
 
-		if deadline == deadline0 {
+		if deadline.Equal(deadline0) {
 			t.Error("deadline didn't change")
 		}