update_engine: Make policy UpdateCheckParams processing easier

Currently there are a ton of arguments from UpdateCheckParams that is
passed around in the udpate_attampter.cc. With this CL UpdateCheckParams
is directy passed and this simplies the logic.

BUG=b:171829801
TEST=cros_workon_make --board reef --test update_enigne

Change-Id: If454f6393fc6e28d41fa5d14d184f0db32e8bd19
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2504453
Commit-Queue: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
diff --git a/update_manager/policy.h b/update_manager/policy.h
index 4b3bfc7..ad6994c 100644
--- a/update_manager/policy.h
+++ b/update_manager/policy.h
@@ -43,21 +43,22 @@
 // Parameters of an update check. These parameters are determined by the
 // UpdateCheckAllowed policy.
 struct UpdateCheckParams {
-  bool updates_enabled;  // Whether the auto-updates are enabled on this build.
+  // Whether the auto-updates are enabled on this build.
+  bool updates_enabled{true};
 
   // Attributes pertaining to the case where update checks are allowed.
   //
   // A target version prefix, if imposed by policy; otherwise, an empty string.
   std::string target_version_prefix;
   // Specifies whether rollback images are allowed by device policy.
-  bool rollback_allowed;
+  bool rollback_allowed{false};
   // Specifies if rollbacks should attempt to preserve some system state.
-  bool rollback_data_save_requested;
+  bool rollback_data_save_requested{false};
   // Specifies the number of Chrome milestones rollback should be allowed,
   // starting from the stable version at any time. Value is -1 if unspecified
   // (e.g. no device policy is available yet), in this case no version
   // roll-forward should happen.
-  int rollback_allowed_milestones;
+  int rollback_allowed_milestones{0};
   // Whether a rollback with data save should be initiated on channel
   // downgrade (e.g. beta to stable).
   bool rollback_on_channel_downgrade{false};
@@ -67,7 +68,7 @@
   std::string lts_tag;
 
   // Whether the allowed update is interactive (user-initiated) or periodic.
-  bool interactive;
+  bool interactive{false};
 };
 
 // Input arguments to UpdateCanStart.