cosmetic: vlr_auth_fsm: clarify decision on UMTS AKA or GSM AKA

The code deciding on whether UMTS AKA is used was cascaded and convoluted. By
flattening the decisions, they become easier to read and possibly catch more
weird corner cases / log information more clearly.

- First decide what AKA the RES length reflects.
- Then decide whether all prerequisites for UMTS AKA are satisfied.
- Finally, on UTRAN, turn down the auth if we don't have UMTS AKA, and neatly
  log all of the potential causes.

One corner case that should never occur is that the UMTS AKA RES length is
actually the same length as the GSM AKA SRES. If this nevertheless occurs, log
this as an error, though not turning down authentication because of it. (The
effect is that we would favor UMTS AKA when it has a res_len == sizeof(sres)
and would not succeed to GSM AKA. At least the log will tell us why, now.)

Adjust an expected test output, trivial logging difference.

Change-Id: I43f7f301ea85e518bac91f707391a53182e54fab

0 files changed, 0 insertions, 0 deletions