runtime/race: fix test in preparation for new race runtime

New race runtime is more scrupulous about env flags format.

Change-Id: I2828bc737a8be3feae5288ccf034c52883f224d8
Reviewed-on: https://go-review.googlesource.com/4811
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: dvyukov

src/runtime/race/race_test.go

@@ -152,7 +152,7 @@ func runTests() ([]byte, error) {
 		}
 		cmd.Env = append(cmd.Env, env)
 	}
-	cmd.Env = append(cmd.Env, `GORACE="suppress_equal_stacks=0 suppress_equal_addresses=0 exitcode=0"`)
+	cmd.Env = append(cmd.Env, `GORACE=suppress_equal_stacks=0 suppress_equal_addresses=0 exitcode=0`)
 	return cmd.CombinedOutput()
 }