Keep local reference to KeyguardStatusViewManager so it doesn't get GC'd

This fixes a bug where we'd stop updating the status view in keyguard
because KeyguardStatusViewManager had no references.

It also fixes a bug where KeyguardUpdateMonitor wasn't removing objects
because objects were being compared with WeakReferences rather than the
content of the WeakReferences.

Bug:7095359

Change-Id: I2d9df6097b2270655ad3662bcf7a6757e0515363