Increase UDP test timeout to 1200s

This is because the ESP8266 is now waiting for SEND OK and takes much
more to complete the send_repeat, and echo_burst tests in RAAS.
(but has higher pass ratio).

Author: michalpasztamobica

TESTS/netsocket/udp/udp_tests.h

@@ -43,7 +43,7 @@ namespace udp_global {
 #ifdef MBED_GREENTEA_TEST_UDPSOCKET_TIMEOUT_S
 static const int TESTS_TIMEOUT = MBED_GREENTEA_TEST_UDPSOCKET_TIMEOUT_S;
 #else
-static const int TESTS_TIMEOUT = 480;
+static const int TESTS_TIMEOUT = (20 * 60);
 #endif
 
 static const int MAX_SEND_SIZE_IPV4 = 536;