net: align temporary file, directory names in tests

Also adds missing temporary file deletion.

Change-Id: Ia644b0898022e05d2f5232af38f51d55e40c6fb5
Reviewed-on: https://go-review.googlesource.com/9772Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/dnsclient_unix_test.go

@@ -101,7 +101,7 @@ type resolvConfTest struct {
 }
 
 func newResolvConfTest(t *testing.T) *resolvConfTest {
-	dir, err := ioutil.TempDir("", "resolvConfTest")
+	dir, err := ioutil.TempDir("", "go-resolvconftest")
 	if err != nil {
 		t.Fatal(err)
 	}

src/net/error_test.go

@@ -524,10 +524,11 @@ func TestFileError(t *testing.T) {
 		t.Skip("not supported on %s", runtime.GOOS)
 	}
 
-	f, err := ioutil.TempFile("", "nettest")
+	f, err := ioutil.TempFile("", "go-nettest")
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer os.Remove(f.Name())
 	defer f.Close()
 
 	c, err := FileConn(f)

src/net/mockserver_test.go

@@ -18,7 +18,7 @@ import (
 // It also uses /tmp directory in case it is prohibited to create UNIX
 // sockets in TMPDIR.
 func testUnixAddr() string {
-	f, err := ioutil.TempFile("", "nettest")
+	f, err := ioutil.TempFile("", "go-nettest")
 	if err != nil {
 		panic(err)
 	}