Fix assorted rspec failures due to stale, cached user permissions

RequestStore is disabled in tests, but the Ability class was
caching user permissions based on the user and project ID of
previous test runs. Revise code to use RequestStore only if it
is active.

app/models/ability.rb

@@ -166,10 +166,17 @@ class Ability
     end
 
     def project_abilities(user, project)
-      rules = []
       key = "/user/#{user.id}/project/#{project.id}"
 
-      RequestStore.store[key] ||= begin
+      if RequestStore.active?
+        RequestStore.store[key] ||= uncached_project_abilities(user, project)
+      else
+        uncached_project_abilities(user, project)
+      end
+    end
+
+    def uncached_project_abilities(user, project)
+      rules = []
       # Push abilities on the users team role
       rules.push(*project_team_rules(project.team, user))
 
@@ -198,7 +205,6 @@ class Ability
 
       rules - project_disabled_features_rules(project)
     end
-    end
 
     def project_team_rules(team, user)
       # Rules based on role in project