UDP echotests hold 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

@@ -100,7 +100,6 @@ void UDPSOCKET_ECHOTEST_impl(bool use_sendto)
                 packets_sent++;
             } else {
                 tr_warn("[Round#%02d - Sender] error, returned %d", s_idx, sent);
-                continue;
             }
 
             do {
@@ -207,7 +206,6 @@ void UDPSOCKET_ECHOTEST_NONBLOCK_impl(bool use_sendto)
                 --retry_cnt;
             } else {
                 tr_warn("[Round#%02d - Sender] error, returned %d", s_idx, sent);
-                continue;
             }
 
             int recvd;

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;
             }