PCU_Tests_SNS: improve SGSN originated BVC-RESETs

The BVC-RESETs are a little bit more complicated. The PCU will send
a BVC-RESET after the NSE become available.
Ensure the RESET is received and ignored so there is no race condition
if both sides send a BVC-RESET at the same time.

The test case TC_sns_1c1u_so_bvc_reset is still failing because the PCU can't
handle BVC-RESETs properly (both PTP and signalling).

Change-Id: Id681749d75073c1d50a4b0a2e86f0a2dd0955b45
2 files changed