Deflake Lockscreen Clock Screenshot Tests

Disabling the TextAnimator when animation is disabled should produce
consistent text between runs of the screenshot test.

Fixes: 243942947
Test: atest KeyguardClockSwitchScreenshotTest
Change-Id: Ifaa060a1212331756ad412f1e6027c140fa35921
Merged-In: Ifaa060a1212331756ad412f1e6027c140fa35921