Add new line disappearing animation to LockPatternView.

Instead of simply fading out the line now it disappears with moving gradient.
According to the specs animation delay is 150ms and duration 500ms.

Bug: 196067470
Bug: 193417780
Tests: Manually
Change-Id: If4315683ba73895a0ca8287047d13da150727366
(cherry picked from commit 8392f9c4ac9505c79a4fe3c6f29ee4e24eaf4e3c)