Reuse the code_review_user Prolog rule across gerrit_owners.pl

The condition of a user being the approver of a change
is encapsulated in the code_review_user/1 rule and can be
therefore reused across the whole gerrit_owners.pl for avoiding
duplication of the logic for path and matchers' owners definition.

Change-Id: I4f411f3b978e4547ebab7c0453321c36c38d6542

owners/src/main/prolog/gerrit_owners.pl

diff --git a/owners/src/main/prolog/gerrit_owners.pl b/owners/src/main/prolog/gerrit_owners.pl
index 1fe2a22..b072e82 100644
--- a/owners/src/main/prolog/gerrit_owners.pl
+++ b/owners/src/main/prolog/gerrit_owners.pl
@@ -38,8 +38,8 @@
 add_owner_approval(_, In, Out) :- In = Out.
 
 owner_approved(Path) :-
-  owner(Path, User),
-  gerrit:commit_label(label('Code-Review', 2), User),
+  owner(Path, user(US)),
+  code_review_user(US),
   !.
 
 owner_approved(Users, Path) :-