udp_proxy_wrapper.sh: fix cleanup not cleaning up
udp_proxy_wrapper.sh: fix cleanup not cleaning up

Fixed cleanup leaving the actual udp_proxy behind and only killing an
intermediate shell process.

Fixed trap handler cleaning up but then not dying.

Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls