update_engine: Use GetDlcsToUpdate() instead of GetInstalled()

The meaning of GetInstalled() DBus in dlcservice have changed. So we need
to get the list of DLCs that ought to be updated from the new DBus
GetDlcsToUpdate().

Also rename all dlc_module_ids to dlc_ids.

BUG=chromium:1071654
TEST=cros_workon_make --board reef --test update_engine

Cq-Depend: chromium:2157669
Change-Id: I02e450a1fd75f8b387eb8a107c9c8a32f3e01e6e
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2163441
Tested-by: Amin Hassani <[email protected]>
Reviewed-by: Andrew Lassalle <[email protected]>
Reviewed-by: Jae Hoon Kim <[email protected]>
Commit-Queue: Amin Hassani <[email protected]>
diff --git a/mock_update_attempter.h b/mock_update_attempter.h
index 9d966d7..fdeba52 100644
--- a/mock_update_attempter.h
+++ b/mock_update_attempter.h
@@ -55,7 +55,7 @@
                     UpdateAttemptFlags flags));
 
   MOCK_METHOD2(CheckForInstall,
-               bool(const std::vector<std::string>& dlc_module_ids,
+               bool(const std::vector<std::string>& dlc_ids,
                     const std::string& omaha_url));
 
   MOCK_METHOD2(SetDlcActiveValue, bool(bool, const std::string&));