Enable upgrading persistent APKs on boot.

Bug: 131046856
Test: marked the NetworkStack APK as persistent, verified that
without this patch:
  - adb install networkstack.apk fails
  - adb install --staged networkstack.apk fails (after reboot)
with this patch:
  - adb install networkstack.apk fails
  - adb install --staged networkstack.apk succeds (after reboot)
Change-Id: I346d772e1f4aed94f6faead3b6455efc4666b651

services/core/java/com/android/server/pm/PackageManagerService.java

@@ -939,6 +939,7 @@ public class PackageManagerService extends IPackageManager.Stub
     ComponentName mCustomResolverComponentName;
 
     boolean mResolverReplaced = false;
+    boolean mOkToReplacePersistentPackages = false;
 
     private final @Nullable ComponentName mIntentFilterVerifierComponent;
     private final @Nullable IntentFilterVerifier<ActivityIntentInfo> mIntentFilterVerifier;
@@ -17324,7 +17325,8 @@ public class PackageManagerService extends IPackageManager.Stub
                                         + " target SDK " + oldTargetSdk + " does.");
                     }
                     // Prevent persistent apps from being updated
-                    if ((oldPackage.applicationInfo.flags & ApplicationInfo.FLAG_PERSISTENT) != 0) {
+                    if (((oldPackage.applicationInfo.flags & ApplicationInfo.FLAG_PERSISTENT) != 0)
+                            && !mOkToReplacePersistentPackages) {
                         throw new PrepareFailure(PackageManager.INSTALL_FAILED_INVALID_APK,
                                 "Package " + oldPackage.packageName + " is a persistent app. "
                                         + "Persistent apps are not updateable.");
@@ -21505,10 +21507,12 @@ public class PackageManagerService extends IPackageManager.Stub
 
         mModuleInfoProvider.systemReady();
 
+        mOkToReplacePersistentPackages = true;
         // Installer service might attempt to install some packages that have been staged for
         // installation on reboot. Make sure this is the last component to be call since the
         // installation might require other components to be ready.
         mInstallerService.restoreAndApplyStagedSessionIfNeeded();
+        mOkToReplacePersistentPackages = false;
     }
 
     public void waitForAppDataPrepared() {