Change initial value of mStaleScanResults to true.

In ag/2409026 we introduced a stale scan result bit to prevent callbacks
from sticky broadcasts from occuring until we have fetched the latest
set of scan results. However, this initial value was set to false hence
there is a race condition in which the currently connected network can
still be shown without any other networks, as the scan results have not
yet been processed.

By changing the initial value to true, we address this race condition.

Bug: b/62493360
Test:  runtest --path
frameworks/base/packages/SettingsLib/tests/integ/src/com/android/settingslib/wifi/WifiTrackerTest.java

Change-Id: I5f2108e17d2c549e2176ccf64e640fbd4808b5f1