feat: CanAddPeerEdge is moved to the end of filter (#3036)

Signed-off-by: Gaius <gaius.qi@gmail.com>

scheduler/scheduling/scheduling.go

@@ -516,12 +516,6 @@ func (s *scheduling) filterCandidateParents(peer *resource.Peer, blocklist set.S
 			continue
 		}
 
-		// Candidate parent can add edge with peer.
-		if !peer.Task.CanAddPeerEdge(candidateParent.ID, peer.ID) {
-			peer.Log.Debugf("can not add edge with parent %s", candidateParent.ID)
-			continue
-		}
-
 		// Candidate parent host is not allowed to be the same as the peer host,
 		// because dfdaemon cannot handle the situation
 		// where two tasks are downloading and downloading each other.
@@ -562,6 +556,12 @@ func (s *scheduling) filterCandidateParents(peer *resource.Peer, blocklist set.S
 			continue
 		}
 
+		// Candidate parent can add edge with peer.
+		if !peer.Task.CanAddPeerEdge(candidateParent.ID, peer.ID) {
+			peer.Log.Debugf("can not add edge with parent %s", candidateParent.ID)
+			continue
+		}
+
 		candidateParents = append(candidateParents, candidateParent)
 		candidateParentIDs = append(candidateParentIDs, candidateParent.ID)
 	}