TC_mme_pool_reject_fallback S1GW_Tests

Failing for the past 9 builds since #526

Took 15 sec (from Titan)

Stack Trace

Timeout waiting for CONN_DOWN from pool server 0
      S1GW_Tests.ttcn:1407 S1GW_Tests control part
      S1GW_Tests.ttcn:1069 TC_mme_pool_reject_fallback testcase