ssl_server2.c: fix build err (key_slot - unused variable)
ssl_server2.c: fix build err (key_slot - unused variable)

Signed-off-by: Przemyslaw Stekiel <1d381786fa074b2f2333843496828c8e4357e75f@mobica.com>

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