northd: Initialize hmap size in lflow_mgr.

When (re)starting ovn-northd with an existing big nbdb,
the first iteration of northd was very slow as trying to
push all flows in a single bucket.

Fixes: a623606 ("northd: Refactor lflow management into a separate module.")
Signed-off-by: Xavier Simonart <xsimonar@redhat.com>
Signed-off-by: Numan Siddique <numans@ovn.org>

northd/lflow-mgr.c

@@ -259,6 +259,9 @@ lflow_table_sync_to_sb(struct lflow_table *lflow_table,
     struct hmap *lflows = &lflow_table->entries;
     struct ovn_lflow *lflow;
 
+    fast_hmap_size_for(&lflows_temp,
+                       lflow_table->max_seen_lflow_size);
+
     /* Push changes to the Logical_Flow table to database. */
     const struct sbrec_logical_flow *sbflow;
     SBREC_LOGICAL_FLOW_TABLE_FOR_EACH_SAFE (sbflow, sb_flow_table) {