One sec UDP echotests pause in case of no memory or device busy status.

This  gives possibility of freeing memory and mesh device recover from busy state.

Author: tymoteuszblochmobica

TESTS/netsocket/udp/udpsocket_echotest.cpp

@@ -94,6 +94,9 @@ void UDPSOCKET_ECHOTEST_impl(bool use_sendto)
             } else {
                 sent = sock.send(tx_buffer, pkt_s);
             }
+            if (sent == NSAPI_ERROR_NO_MEMORY) {
+                ThisThread::sleep_for(1000);
+            }
             if (check_oversized_packets(sent, pkt_s)) {
                 TEST_IGNORE_MESSAGE("This device does not handle oversized packets");
             } else if (sent == pkt_s) {

TESTS/netsocket/udp/udpsocket_sendto_repeat.cpp

@@ -41,7 +41,7 @@ void UDPSOCKET_SENDTO_REPEAT()
     bool oom_earlier = false; // 2 times in a row -> time to give up
     for (i = 0; i < 100; i++) {
         sent = sock.sendto(udp_addr, tx_buffer, sizeof(tx_buffer));
-        if (sent == NSAPI_ERROR_NO_MEMORY) {
+        if (sent == NSAPI_ERROR_NO_MEMORY || sent == NSAPI_ERROR_BUSY) {
             if (oom_earlier) {
                 break;
             }