Change AccessPointPreference key generation to match AccessPoint.

AccessPointPreference now uses SSID + security to determine preference
key, which matches the way WifiTracker groups scan results. This
prevents mismatches between WifiSettings and WifiTracker.

Bug: 64887518
Test: make -40 RunSettingsLibRoboTests
Change-Id: I021a266cbb1037b7ac82efc72f0670088a521640
2 files changed