Reset killedByAm flag at attachApplicationLocked

Cherry picked from aosp.

Fixes bug 18593309.

ActivityManager reuses a process record object that killed
by him under some situation. That reused process record inherits
a killedByAm flag unexpectedly.
The killedByAm flag must be reset otherwise ActivityManager can't
judge the process can be killed or not.

Change-Id: If95137d91939cc44882ad2813131bcde0edd0c1b
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 6823119..2c916da 100755
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -5878,6 +5878,7 @@
         app.hasShownUi = false;
         app.debugging = false;
         app.cached = false;
+        app.killedByAm = false;
 
         mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);