CI: fixig failing OAI UE + USRP + OAI eNB test

  -- scenarios were using FDD 5MHz conf file w/ active RRC inactivity timeout
  -- since we are waiting very long that UE is sync'ed w/ eNB, timeout occurs and UE is released
  -- solution is to disable timeouts in command line in scenario
  -- also python is fixed to handle properly wrong ping exits

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>