message: fix the unused variable warning
  /eos/plugins/chain_plugin/include/eos/chain_plugin/chain_plugin.hpp:222:12: warning: unused variable 'start'
  [-Wunused-variable]
  auto start = fc::time_point::now();
  ^
diff: @@ -219,7 +219,6 @@ public:
  vector<char> data;
  - auto start = fc::time_point::now();
  auto end = fc::time_point::now() + fc::microseconds( 1000*10 ); /// 10ms max time
  int count = 0;
  