Don't reset timer during mbedtls_ssl_setup()

At that point, the timer might not yet be configured.

The timer is reset at the following occasions:

- when it is initially configured through
    mbedtls_ssl_set_timer_cb() or
    mbedtls_ssl_set_timer_cb_cx()
- when a session is reset in mbedtls_ssl_session_reset()
- when a handshake finishes via mbedtls_ssl_handshake_wrap()

library/ssl_tls.c

@@ -7777,8 +7777,6 @@ static int ssl_handshake_init( mbedtls_ssl_context *ssl )
             ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_PREPARING;
         else
             ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_WAITING;
-
-        ssl_set_timer( ssl, 0 );
     }
 #endif