[WIFI][PASSPOINT] Fix parsing of Interworking IE

The Interworking IE parser assumed that the optional Venue Info
field was not present. This resulted in an invalid HESSID value
when the Venue Info was present.

Bug: 67845093
Test: unit tests (including added one) pass
Change-Id: If9a9816ae7d6ee55f9cc82a93d25b42cdee6981d
2 files changed