[core] re-enable overloaded backends w/ multi wkrs

re-enable overloaded backends when server.max-worker is non-zero

(thx jens-maus)

x-ref:
  "mod_proxy not re-enabling proxy with 1.4.48" (multiple workers)
  https://redmine.lighttpd.net/boards/2/topics/7906

src/gw_backend.c

@@ -2488,17 +2488,31 @@ static void gw_handle_trigger_exts(server *srv, gw_exts *exts, int debug) {
     }
 }
 
+static void gw_handle_trigger_exts_wkr(server *srv, gw_exts *exts) {
+    for (size_t j = 0; j < exts->used; ++j) {
+        gw_extension * const ex = exts->exts[j];
+        for (size_t n = 0; n < ex->used; ++n) {
+            gw_host * const host = ex->hosts[n];
+            for (gw_proc *proc = host->first; proc; proc = proc->next) {
+                if (proc->state == PROC_STATE_OVERLOADED)
+                    gw_proc_check_enable(srv, host, proc);
+            }
+        }
+    }
+}
+
 handler_t gw_handle_trigger(server *srv, void *p_d) {
     gw_plugin_data *p = p_d;
-    if (0 != srv->srvconf.max_worker && p->srv_pid != srv->pid)
-        return HANDLER_GO_ON;
+    int wkr = (0 != srv->srvconf.max_worker && p->srv_pid != srv->pid);
 
     for (size_t i = 0; i < srv->config_context->used; i++) {
         gw_plugin_config *conf = p->config_storage[i];
         gw_exts *exts = conf->exts;
         int debug = conf->debug ? conf->debug : p->config_storage[0]->debug;
         if (NULL == exts) continue;
-        gw_handle_trigger_exts(srv, exts, debug);
+        wkr
+          ? gw_handle_trigger_exts_wkr(srv, exts)
+          : gw_handle_trigger_exts(srv, exts, debug);
     }
 
     return HANDLER_GO_ON;