Ensure BSSIDs are correctly aged out in settings view

When verbose logging is on, recent BSSIDs are displayed under the
network. This ensures that the BSSIDs are aged out after a period of
time instead of based on a fixed size LRU cache. This prevents BSSIDs
that are no longer present from appearing in the results.

FIXED=30711015
TEST=setup two APs, observe both BSSIDs in settings, turn off one,
     observe it disappearing after a short period of time.

Change-Id: Id2b2ccd0899eae8d4e2e1c2b3ae9409136a8c948
(cherry picked from commit b744d6e8)