wifi: only keep PMK cache for predictable disconnection case.

Losing PMK cache only results in addtional connection time, but
keeping PMK cache might lead to unexpected connection issues due to
access point compatibilities.

Bug: 184414469
Test: atest FrameworksWifiTests
Change-Id: Ibc005690cf119450fca75bbeb55a572df52f5bf7
1 file changed