Update method of getting ScanResult of current network.

Noticed that ScanResult got from ScanDetailCache associated with
provided BSSID would be null if forcing to forget and then reconnet
to the wifi network. This would cause IpClient get null ScanResult.
Update the method of getting ScanResult with a more robust way.

Bug: 137835398
Test: atest FrameworksWifiTests
Change-Id: I3ea5a301a9635248a2d121d9a6b7493cc6f430a6
1 file changed