Fix LockSettingsServiceTest

* Mock out registerReceiverAsUser() to avoid SecurityException
* Mock out setKeystorePassword() to not call into the real keystore

Bug: 170661840
Test: atest com.android.server.locksettings
Change-Id: I97c33f3b21ac16d2bb92e1658c222e4d0fd1970e
3 files changed