DOC: management: add init-state to add server keywords

Commit ce6a621 allowed init-state to be used for dynamic servers but I
forgot to update management doc.

Author: dclaisse

doc/management.txt

@@ -1730,6 +1730,7 @@ add server <backend>/<server> [args]*
   - fastinter
   - force-sslv3/tlsv10/tlsv11/tlsv12/tlsv13
   - id
+  - init-state
   - inter
   - maxconn
   - maxqueue