revocation: Enforce a (configurable) timeout when fetching OCSP/CRL

Malicious servers could otherwise block the fetching thread indefinitely
after the initial TCP handshake (which has a default timeout of 10s
in the curl and winhttp plugins, the soup plugin actually has a default
overall timeout of 10s).

src/libstrongswan/plugins/files/files_fetcher.c

@@ -82,6 +82,9 @@ METHOD(fetcher_t, set_option, bool,
 			this->cb = va_arg(args, fetcher_callback_t);
 			break;
 		}
+		case FETCH_TIMEOUT:
+			/* irrelevant, but fine if requested */
+			break;
 		default:
 			supported = FALSE;
 			break;