fix aggressive expiration detection (#11446)

for some flaky networks this may be too fast of a value
choose a defensive value, and let this be addressed
properly in a new refactor of dsync with renewal logic.

Also enable faster fallback delay to cater for misconfigured
IPv6 servers

refer
 - https://golang.org/pkg/net/#Dialer
 - https://tools.ietf.org/html/rfc6555

cmd/local-locker.go

@@ -258,7 +258,7 @@ func (l *localLocker) Expired(ctx context.Context, args dsync.LockArgs) (expired
 				ep := globalRemoteEndpoints[args.Owner]
 				if !ep.IsLocal {
 					// check if the owner is online
-					return isServerResolvable(ep, 250*time.Millisecond) != nil, nil
+					return isServerResolvable(ep, 1*time.Second) != nil, nil
 				}
 				return false, nil
 			}