update_engine: Indicate existence of owner instead of owner's email in log.

Logging the device owner's email is possibly a PII, so instead log
whether the device has a owner as a boolean value.

Enterprise devices do not have a device owner.

The variable var_has_owner is dependent on DevicePolicy::GetOwner().

BUG=chromium:973108
TEST=unittest

Change-Id: I535f664a4fcf75c6102346b8566605710b062255
Reviewed-on: https://chromium-review.googlesource.com/1660911
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Ready: 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/update_manager/chromeos_policy.cc b/update_manager/chromeos_policy.cc
index bdb88f8..08c355e 100644
--- a/update_manager/chromeos_policy.cc
+++ b/update_manager/chromeos_policy.cc
@@ -555,8 +555,9 @@
     if (policy_au_p2p_enabled_p) {
       enabled = *policy_au_p2p_enabled_p;
     } else {
-      const string* policy_owner_p = ec->GetValue(dp_provider->var_owner());
-      if (!policy_owner_p || policy_owner_p->empty())
+      const bool* policy_has_owner_p =
+          ec->GetValue(dp_provider->var_has_owner());
+      if (!policy_has_owner_p || !*policy_has_owner_p)
         enabled = true;
     }
   }