Fix 4518876: Disable lock screen rotation on phones.

This reverts commit e28016c2
that enabled lockscreen rotation always and works around a
race condition caused by KeyguardViewManager not following
onConfigurationChanged events.  It now checks
R.bool.config_enableLockScreenRotation each time it is shown.

There's still some work to be done, but this change makes the
phone usable.  KeyguardViewManager needs to track config
changes and update the layout parameters to be correct.

Change-Id: I7c9f2402c960d5bd72a4b73118a66e27a05777cf