Fix Mux Connect Error (#18567)

`OpMuxConnectError` was not handled correctly.

Remove local checks for single request handlers so they can 
run before being registered locally.

Bonus: Only log IAM bootstrap on startup.

cmd/erasure-server-pool.go

@@ -1967,7 +1967,7 @@ func (z *erasureServerPools) Walk(ctx context.Context, bucket, prefix string, re
 				go func() {
 					defer wg.Done()
 
-					disks, _ := set.getOnlineDisksWithHealing()
+					disks, _ := set.getOnlineDisksWithHealing(true)
 					if len(disks) == 0 {
 						cancel()
 						return