upstream_conn: fix ordering of mk_event_inject and prepare_conn_destroy

prepare_destroy_conn calls mk_list_del on the event in the
priority bucket queue, so for safety, we inject it after
this covers us against the case where the event was triggered
and waiting, but we also reached the timeout.

Signed-off-by: Wesley Pettit <wppttt@amazon.com>

Author: PettitWesley

src/flb_upstream.c

@@ -794,6 +794,7 @@ int flb_upstream_conn_timeouts(struct mk_list *list)
 {
     time_t now;
     int drop;
+    int inject;
     struct mk_list *head;
     struct mk_list *u_head;
     struct mk_list *tmp;
@@ -842,13 +843,21 @@ int flb_upstream_conn_timeouts(struct mk_list *list)
             }
 
             if (drop == FLB_TRUE) {
+                inject = FLB_FALSE;
                 if (u_conn->event.status != MK_EVENT_NONE) {
+                    inject = FLB_TRUE;
+                }
+                u_conn->net_error = ETIMEDOUT;
+                prepare_destroy_conn(u_conn);
+                /* 
+                 * prepare_destroy_conn calls mk_list_del on the event in the 
+                 * priority bucket queue, so for safety, we inject it afterwards
+                 */
+                if (inject == FLB_TRUE) {
                     mk_event_inject(u_conn->evl, &u_conn->event,
                                     MK_EVENT_READ | MK_EVENT_WRITE,
                                     FLB_TRUE);
                 }
-                u_conn->net_error = ETIMEDOUT;
-                prepare_destroy_conn(u_conn);
             }
         }