Unexpected log field

[rleungx]

Bug Report

Error: 4/06 05:50:15.661 +00:00] [ERROR] [pd_service_discovery.go:221] ["[pd] failed to update member"] [error="[PD:client:ErrClientGetMember]get member failed%!(EXTRA []string=[http://127.0.0.1:32879/ http://127.0.0.1:37741/ [http://127.0.0.1:41645])](http://127.0.0.1:41645]%29/)"]
Error: 4/06 05:50:15.661 +00:00] [ERROR] [pd_service_discovery.go:221] ["[pd] failed to update member"] [error="[PD:client:ErrClientGetMember]get member failed%!(EXTRA []string=[http://127.0.0.1:32879/ http://127.0.0.1:37741/ [http://127.0.0.1:41645])](http://127.0.0.1:41645]%29/)"]

The log is not well readable by misusing FastGenByArgs which is introduced by #6046