idgen: correct comments for id generator
Comments for id generator format is out of
date, correct it.
Fixes
@@ -32,8 +32,8 @@ const (
// a node member ID.
//
// The initial id is in this format:
-// High order byte is memberID, next 5 bytes are from timestamp,
-// and low order 2 bytes are 0s.
+// High order 2 bytes are from memberID, next 5 bytes are from timestamp,
+// and low order one byte is a counter.
// | prefix | suffix |
// | 2 bytes | 5 bytes | 1 byte |
// | memberID | timestamp | cnt |
