Revert "update_engine: Support milestones to EOL from Omaha"

This reverts commit 893cae4b0e5141bcaf9f56b1775e681c8f523630.

Reason for revert: use of EOL date and EOL notification date instead milestones to EOL.

Original change's description:
> update_engine: Support milestones to EOL from Omaha
>
> Initiative to show EOL message on Chrome OS devices require that
> update_engine parses the fields within Omaha response that pertain to the
> new milestones to EOL field. The Omaha response will include a new
> field called "milestones_to_eol" which will be an integer value
> string.
>
> The job of update_engine when it comes to milestones to EOL from Omaha
> is to merely forward. No checks and no modifications of fields are
> done within update_engine besides being able to convert the milestones
> to EOL from a string to integer.
>
> BUG=chromium:994999
> TEST=FEATURES="test" emerge-$BOARD update_engine update_engine-client
> TEST=cros deploy $IP update_engine update_engine-client
> TEST=test_that -b $BOARD $IP autoupdate_EOL # from Cq-Depend
> TEST=test_that -b $BOARD $IP autoupdate_EOL.milestones # from Cq-Depend
>
> Cq-Depend:chromium:1761371
> Change-Id: I268e4c8e641b17d6a727a50f53285cc97c76eb22
> Reviewed-on: https://chromium-review.googlesource.com/1759285
> Tested-by: Jae Hoon Kim <kimjae@chromium.org>
> Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
> Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
> Reviewed-by: Nicolas Norvez <norvez@chromium.org>
> Reviewed-by: Amin Hassani <ahassani@chromium.org>

TBR=maybelle@chromium.org,norvez@chromium.org,ahassani@chromium.org,abutzier@chromium.org,chromiumos-cl-exonerator@appspot.gserviceaccount.com,kimjae@chromium.org

BUG=chromium:994999
TEST=none
Cq-Depend:chromium:1782971
Change-Id: I42e75e22948b3653500d355027dc3312015c9ebf
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/1782970
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/omaha_request_action.cc b/omaha_request_action.cc
index 8da7e29..6c67a3b 100644
--- a/omaha_request_action.cc
+++ b/omaha_request_action.cc
@@ -109,7 +109,6 @@
 
 // updatecheck attributes (without the underscore prefix).
 constexpr char kAttrEol[] = "eol";
-constexpr char kAttrMilestonesToEol[] = "milestones_to_eol";
 constexpr char kAttrRollback[] = "rollback";
 constexpr char kAttrFirmwareVersion[] = "firmware_version";
 constexpr char kAttrKernelVersion[] = "kernel_version";
@@ -1316,28 +1315,13 @@
 
 bool OmahaRequestAction::PersistEolStatus(const map<string, string>& attrs) {
   auto eol_attr = attrs.find(kAttrEol);
-  auto milestones_to_eol_attr = attrs.find(kAttrMilestonesToEol);
-
-  bool ret = true;
-  if (milestones_to_eol_attr == attrs.end()) {
-    system_state_->prefs()->Delete(kPrefsOmahaMilestonesToEol);
-    if (eol_attr != attrs.end()) {
-      LOG(WARNING) << "Milestones to EOL missing when EOL.";
-    }
-  } else if (!system_state_->prefs()->SetString(
-                 kPrefsOmahaMilestonesToEol, milestones_to_eol_attr->second)) {
-    LOG(ERROR) << "Setting milestones to EOL failed.";
-    ret = false;
+  if (eol_attr != attrs.end()) {
+    return system_state_->prefs()->SetString(kPrefsOmahaEolStatus,
+                                             eol_attr->second);
+  } else if (system_state_->prefs()->Exists(kPrefsOmahaEolStatus)) {
+    return system_state_->prefs()->Delete(kPrefsOmahaEolStatus);
   }
-
-  if (eol_attr == attrs.end()) {
-    system_state_->prefs()->Delete(kPrefsOmahaEolStatus);
-  } else if (!system_state_->prefs()->SetString(kPrefsOmahaEolStatus,
-                                                eol_attr->second)) {
-    LOG(ERROR) << "Setting EOL failed.";
-    ret = false;
-  }
-  return ret;
+  return true;
 }
 
 void OmahaRequestAction::ActionCompleted(ErrorCode code) {