HTTP::disable keep cookie persistence

[root@ve10:Active] config  b virtual bar list
virtual bar {
   snat automap
   destination 172.28.19.252:80
   ip protocol 6
   rules myrule
   persist cookie
   profiles {
      http {}
      tcp {}
   }
}
[root@ve10:Active] config  b pool foo list
pool foo {
   members {
      200.200.200.101:80 {}
      200.200.200.111:80 {}
   }
}
[root@ve10:Active] config  b rule myrule list
rule myrule {
   when CLIENT_ACCEPTED {
   log local0. "client [IP::client_addr]:[TCP::client_port]"
}
when HTTP_REQUEST {
   set uri [HTTP::uri]
   if { $uri contains ".gif" } {
      HTTP::disable
      pool foo
   } else {
      pool foo
   }
}
when SERVER_CONNECTED {
   log local0. "client [IP::client_addr]:[TCP::client_port] server [IP::server_addr]:[TCP::server_port]"
}
when HTTP_RESPONSE {
   log local0. "client [IP::client_addr]:[TCP::client_port] server [IP::server_addr]:[TCP::server_port] uri $uri"
}
}

 there were 2 http requests; the 1st one was /index.html (no.1) and the 2nd one was /f5.gif (no.4) with cookie. i assumed it is on different tcp connection, so i created a new tcp connection for 2nd request. the log showd the 2nd request was forwarded to new pool member.

[root@ve10:Active] config  tail -f /var/log/ltm
(1) Apr 23 14:59:42 local/tmm info tmm[4950]: Rule myrule : client 172.28.19.251:50884
(2) Apr 23 14:59:42 local/tmm info tmm[4950]: Rule myrule : client 172.28.19.251:50884 server 200.200.200.101:80
(3) Apr 23 14:59:42 local/tmm info tmm[4950]: Rule myrule : client 172.28.19.251:50884 server 200.200.200.101:80 uri /
(4) Apr 23 14:59:51 local/tmm info tmm[4950]: Rule myrule : client 172.28.19.251:50885
(5) Apr 23 14:59:51 local/tmm info tmm[4950]: Rule myrule : client 172.28.19.251:50885 server 200.200.200.111:80