PGW_Tests: update default values for mp_pgw_hostname/mp_pcrf_local_ip

The old values are not valid anymore when running against open5gs
version 2.4.2.  Most likely, the default addresses got changed
during the PGW split-up (now it's open5gs-smfd and open5gs-upfd).

Change-Id: I3dd7d1f0d4aebb94b8859e8d12e952917de35071
Related: SYS#5602
1 file changed