load_balancer: open db connection from every process

This ensures that the `mi("lb_reload")` command runs properly from
whatever process the job is dispatched from.

Many thanks to Antonis Psaras (@apsaras on GitHub) for reporting it.
Close #3488

(cherry picked from commit 3df04c7)

modules/load_balancer/load_balancer.c

@@ -479,17 +479,17 @@ static int mod_init(void)
 
 static int child_init(int rank)
 {
+ /* init DB connection */
+ if ( lb_connect_db(&db_url)!=0 ) {
+ LM_CRIT("cannot initialize database connection\n");
+ return -1;
+ }
  return 0;
 }
 
 
 static int mi_child_init( void )
 {
- /* init DB connection */
- if ( lb_connect_db(&db_url)!=0 ) {
- LM_CRIT("cannot initialize database connection\n");
- return -1;
- }
  return 0;
 }