update_engine: Store fingerprint value from Omaha response.

Store the unique fp value from response into prefs. Value is later sent
to Omaha to determine if there is a subsequent update available
while the system is waiting to be rebooted.

BUG=b:161259884
TEST=cros_workon_make --board=hatch --test update_engine

Change-Id: Ie37aa5da3cd8a0820e633f5ef426fb50e8a02838
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2491618
Tested-by: Vyshu Khota <vyshu@google.com>
Commit-Queue: Vyshu Khota <vyshu@google.com>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/cros/omaha_response_handler_action.cc b/cros/omaha_response_handler_action.cc
index b6c223f..52142a3 100644
--- a/cros/omaha_response_handler_action.cc
+++ b/cros/omaha_response_handler_action.cc
@@ -106,7 +106,9 @@
          .metadata_signature = package.metadata_signature,
          .hash = raw_hash,
          .type = package.is_delta ? InstallPayloadType::kDelta
-                                  : InstallPayloadType::kFull});
+                                  : InstallPayloadType::kFull,
+         .fp = package.fp,
+         .app_id = package.app_id});
     update_check_response_hash += package.hash + ":";
   }
   install_plan_.public_key_rsa = response.public_key_rsa;