Set text color in the KeyguardIndication

Instead of directly setting the text color on
the TextView. The text color should be updated
when the TextView animates in the new text to show,
not immediately on receiving a request to show
new text.

Test: atest KeyguardIndicationControllerTest
Fixes: 185439308
Change-Id: I7f0a876f4e06864d4bd555ba9a85279aaad72c77