BUG/MINOR: ssl_ckch: Free error msg if commit changes on a cert entry fails

On the CLI, If we fail to commit changes on a certificate entry, an error
message is returned. This error must be released.

This patch must be backported as far as 2.2.

src/ssl_ckch.c

@@ -2154,6 +2154,7 @@ static int cli_io_handler_commit_cert(struct appctx *appctx)
 		applet_putchk(appctx, trash);
 		free_trash_chunk(trash);
 	}
+	free(err);
 	/* error: call the release function and don't come back */
 	return 1;
 }