helper: shutdown command should return with 0 exit status

Commit a35712a85c caused a regression where command

openocd -c "echo a1; shutdown; echo a2"

always returned non-zero exit status to operating system,
even when commands before shutdown all succeeded. This patch
attempt to fix this.

Change-Id: I3f478c2c51d100af810ea0171d2fd4c8fcc657f3
Signed-off-by: Juha Niskanen <juha.niskanen@haltian.com>
Reviewed-on: http://openocd.zylin.com/2589
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>

src/helper/command.c

@@ -660,7 +660,10 @@ int command_run_line(struct command_context *context, char *line)
 		Jim_DeleteAssocData(interp, "context");
 	}
 	if (retcode == JIM_ERR) {
-		if (retval != ERROR_COMMAND_CLOSE_CONNECTION) {
+		if (retval == ERROR_COMMAND_CLOSE_CONNECTION) {
+			/* Shutdown request is not an error */
+			return ERROR_OK;
+		} else {
 			/* We do not print the connection closed error message */
 			Jim_MakeErrorMessage(interp);
 			LOG_USER("%s", Jim_GetString(Jim_GetResult(interp), NULL));