Emit fingerprints during OTA upgrades.

Can be used to help confirm diagnosis of bugs like 34525014.

Test: builds, boots
Bug: 36795529
Change-Id: Ie2517061ef031716c493b2544b0fb95628f20737
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index 6b6adc3..c4d6ec0 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -2385,6 +2385,10 @@
 
             final VersionInfo ver = mSettings.getInternalVersion();
             mIsUpgrade = !Build.FINGERPRINT.equals(ver.fingerprint);
+            if (mIsUpgrade) {
+                logCriticalInfo(Log.INFO,
+                        "Upgrading from " + ver.fingerprint + " to " + Build.FINGERPRINT);
+            }
 
             // when upgrading from pre-M, promote system app permissions from install to runtime
             mPromoteSystemApps =