ofproto-dpif: fix an ovs crash when dpif_recv_set returns error

When dpif_recv_set returns an error, close_dpif_backer gets called,
which in term calls recirc_id_pool_destroy, which can lead to a crash
since recirc_id_pool_create() was not called before this patch.

Reported-by: Mukesh Hira <mhira@vmware.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>