Terminate block production loop when shutting down witness plugin bitshares#1314

Author: cogutvalera

libraries/plugins/witness/include/graphene/witness/witness.hpp

@@ -84,6 +84,7 @@ class witness_plugin : public graphene::app::plugin {
 
    boost::program_options::variables_map _options;
    bool _production_enabled = false;
+   bool _shutting_down = false;
    uint32_t _required_witness_participation = 33 * GRAPHENE_1_PERCENT;
    uint32_t _production_skip_flags = graphene::chain::database::skip_nothing;
 

libraries/plugins/witness/witness.cpp

@@ -144,6 +144,7 @@ void witness_plugin::plugin_startup()
 void witness_plugin::plugin_shutdown()
 {
    // nothing to do
+   _shutting_down = true;
 }
 
 void witness_plugin::refresh_witness_key_cache()
@@ -161,6 +162,8 @@ void witness_plugin::refresh_witness_key_cache()
 
 void witness_plugin::schedule_production_loop()
 {
+   if (_shutting_down) return;
+
    //Schedule for the next second's tick regardless of chain state
    // If we would wait less than 50ms, wait for the whole second.
    fc::time_point now = fc::time_point::now();