fix uninitialization issue in JankTracker

We should initialize mSwapDeadline in JankTracker, or it can be a very
large randomized value and then makes jank tracker not collect concrete
jank type of frames appropriately as expected.

Bug: 161656795
Test: run cts -m CtsIncidentHostTestCases -t
   com.android.server.cts.GraphicsStatsValidationTest#testJankyDrawFrame
Change-Id: I057a50a74502918619204f9164f6a954f8e9c5de