Reset the subreason field while reusing the AppExitInfoTracker record

Bug: 222752166
Test: manual - dumpsys activity exit-info
Change-Id: I131aee7a87290b0dc31688f9eb779f2f1772237a

services/core/java/com/android/server/am/AppExitInfoTracker.java

@@ -1002,6 +1002,7 @@ public final class AppExitInfoTracker {
             info.setPackageName(app.info.packageName);
             info.setPackageList(app.getPackageList());
             info.setReason(ApplicationExitInfo.REASON_UNKNOWN);
+            info.setSubReason(ApplicationExitInfo.SUBREASON_UNKNOWN);
             info.setStatus(0);
             info.setImportance(procStateToImportance(app.mState.getReportedProcState()));
             info.setPss(app.mProfile.getLastPss());