Added encryption simulation in dbsim

Option --encryption=1 enables encryption simulation in dbsim. The
`do_crypt()` callback flips bits of input buffer and writes to output.

dbsim/db_simulator.cpp

@@ -140,7 +140,7 @@ void db::simulator::start()
         std::string server_options(params_.wsrep_provider_options);
 
         if (server.server_state().load_provider(
-                params_.wsrep_provider, server_options, false))
+                params_.wsrep_provider, server_options, params_.encryption))
         {
             throw wsrep::runtime_error("Failed to load provider");
         }