SGSN_Tests: Wait for RAU Accept after receiving SecurityModeCmd

We don't want to pass the test or return from this function before
receiving a RAU accept. With Iu we expect a Security Mode
Command/Complete before the routing area is updated, but we do want to
wait for the actual RAU Accept or fail when receiving a RAU Reject.

Change-Id: Id89e2c6dae8cbdb5e8dee1c92960dc3346590a95
Related: OS#3727
1 file changed