Fix build error on invalid build list, reset builder on restart

app/jobs/abf_worker/rpm_worker_observer.rb

@@ -21,8 +21,7 @@ def real_perform
         fill_container_data if status != STARTED
 
         unless subject.valid?
-          subject.build_error(false)
-          subject.save(validate: false)
+          subject.update_attribute(:status, BuildList::BUILD_ERROR)
           return
         end
 
@@ -80,6 +79,7 @@ def restart_task
       else
         Redis.current.lpush RESTARTED_BUILD_LISTS, subject.id
         subject.update_column(:status, BuildList::BUILD_PENDING)
+        subject.update_column(:builder_id, nil)
         return true
       end
     end
@@ -96,4 +96,4 @@ def fill_container_data
     end
 
   end
-end
+end