Close acceptor after shutdown of thread pool so it is safe to access …

…from application thread

plugins/net_plugin/net_plugin.cpp

@@ -3414,12 +3414,6 @@ namespace eosio {
                my->keepalive_timer->cancel();
          }
 
-         if( my->acceptor ) {
-            boost::system::error_code ec;
-            my->acceptor->cancel( ec );
-            my->acceptor->close( ec );
-         }
-
          {
             fc_ilog( logger, "close ${s} connections", ("s", my->connections.size()) );
             std::lock_guard<std::shared_mutex> g( my->connections_mtx );
@@ -3433,6 +3427,13 @@ namespace eosio {
          if( my->thread_pool ) {
             my->thread_pool->stop();
          }
+
+         if( my->acceptor ) {
+            boost::system::error_code ec;
+            my->acceptor->cancel( ec );
+            my->acceptor->close( ec );
+         }
+
          app().post( 0, [me = my](){} ); // keep my pointer alive until queue is drained
          fc_ilog( logger, "exit shutdown" );
       }