update_engine: UM: More permissive use of P2P.

The logic we had in ChromeOSPolicy so far was not as permissive as the
original in P2PManagerImpl::IsP2PEnabled(). Specifically, we want to
allow P2P even if a device policy does not have this value set, but
otherwise indicates that the device is enterprise-enrolled.

This also renames the owner variable name so it is consistent with the
rest of the variable names (no get_ prefix).

BUG=chromium:384087
TEST=Unit tests.

Change-Id: I184ebaebc168352510ea3ed0277ea74167edf666
Reviewed-on: https://chromium-review.googlesource.com/221476
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: David Zeuthen <zeuthen@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/update_manager/device_policy_provider.h b/update_manager/device_policy_provider.h
index ba5d4d9..b0b9d36 100644
--- a/update_manager/device_policy_provider.h
+++ b/update_manager/device_policy_provider.h
@@ -45,7 +45,7 @@
 
   // Variable stating the name of the device owner. For enterprise enrolled
   // devices, this will be an empty string.
-  virtual Variable<std::string>* var_get_owner() = 0;
+  virtual Variable<std::string>* var_owner() = 0;
 
   virtual Variable<bool>* var_http_downloads_enabled() = 0;