Increase ScanResult cache eviction timeout for failed/aborted scans

Currently ScanResults are evicted from WifiTracker's cache when they
are more than 15 seconds old. Since scans are conducted every 10
seconds, one aborted scan will cause no fresh scans to be seen until
20 seconds later, resulting in all scans to be evicted and the
wifi-picker completely emptying.

This change doubles the eviction timeout to 30 seconds if the last
scan was aborted, avoiding this case.

Bug: 113132408
Test: atest WifiTrackerTest
Change-Id: I2e3aad3a1470f52c3d87e657262a2c4de1bd2418