LSS: check whether to cache SP in handler

LockSettingsService should not call DevicePolicyManagerService while
holding a lock this will likely lead to a deadlock. That was the case
here so post to a handler to drop the LSS locks.

Fix: 72538198
Test: runtest frameworks-services -p com.android.server.locksettings
Test: cts-tradefed run cts-dev -m CtsDevicePolicyManagerTestCases -t com.android.cts.devicepolicy
Test: cts-tradefed run cts-dev -m CtsDevicePolicyManagerTestCases \
          -t com.android.cts.devicepolicy.ManagedProfileTest#testResetPasswordTokenUsableAfterClearingLock
Change-Id: I74bdb2a556ff97f6ae76881ca0e13d9a6e0c706f