all: don't call t.Fatal from a goroutine

Fixes #17900.

Change-Id: I42cda6ac9cf48ed739d3a015a90b3cb15edf8ddf
Reviewed-on: https://go-review.googlesource.com/33243
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

handshake_server_test.go

@@ -206,7 +206,8 @@ func TestRenegotiationExtension(t *testing.T) {
 		buf = make([]byte, 1024)
 		n, err := c.Read(buf)
 		if err != nil {
-			t.Fatalf("Server read returned error: %s", err)
+			t.Errorf("Server read returned error: %s", err)
+			return
 		}
 		buf = buf[:n]
 		c.Close()

tls_test.go

@@ -295,12 +295,14 @@ func TestTLSUniqueMatches(t *testing.T) {
 		for i := 0; i < 2; i++ {
 			sconn, err := ln.Accept()
 			if err != nil {
-				t.Fatal(err)
+				t.Error(err)
+				return
 			}
 			serverConfig := testConfig.Clone()
 			srv := Server(sconn, serverConfig)
 			if err := srv.Handshake(); err != nil {
-				t.Fatal(err)
+				t.Error(err)
+				return
 			}
 			serverTLSUniques <- srv.ConnectionState().TLSUnique
 		}