pgw: Add support for PCRF emulation (CCR/CCA)

If mp_pcrf_local_ip is set to a non-empty string, the PGW testsuite
now emulates a PCRF and expects the PGW to perform the related
transactions - so far Credit-Control-Request INITIAL_REQUEST
at session creation, and TERMINATION_REQUST at session deletion.

Change-Id: I5f0c7a66d38e5c8b5f36b45717d49648a14ed7b2
4 files changed