TESTS: Add socket.set_timeout in udpsocket_echotest
TESTS: Add socket.set_timeout in udpsocket_echotest

Some packet loss may be expected/allowed with UDP.
Set socket timeout to continue testing if no response is received within a timeout.

andcor02/mbed-os,mbedmicro/mbed,kjbracey-arm/mbed,kjbracey-arm/mbed,andcor02/mbed-os,mbedmicro/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os