MINOR: backend: rename sample fetch functions and declare the sample keywords

The following sample fetch functions were only usable by ACLs but are now
usable by sample fetches too :

  avg_queue, be_conn, be_id, be_sess_rate, connslots, nbsrv,
  queue, srv_conn, srv_id, srv_is_up, srv_sess_rate

The fetch functions have been renamed "smp_fetch_*".
2 files changed