Initialize isKeyguardEnabled from LockPatternUtils.

The device knows upon boot whether keyguard is enabled or not - defaulting to true is not an accurate reflection of the device state and causes issues when the initial false value comes in after a true emission.

Bug: 278086361
Test: atest SystemUITests
Flag: EXEMPT bugfix
Change-Id: Ic749f8ad0dff8f0ebb7cf02310c4a160a03e6e08