Several fixed in Prepared statements

* is STMT_PREPARE failed when there is a previous status (maybe STMT_EXECUTE) disconnect the client immediately. Maybe this is related to #1366 , but I can't reproduce it yet
* purge prepared statements is also their server reference counter is 0
* initialize connections queue for purging connections

lib/MySQL_HostGroups_Manager.cpp

@@ -831,6 +831,7 @@ MySQL_HostGroups_Manager::MySQL_HostGroups_Manager() {
 	mydb->execute(MYHGM_MYSQL_SERVERS_INCOMING);
 	mydb->execute(MYHGM_MYSQL_REPLICATION_HOSTGROUPS);
 	mydb->execute(MYHGM_MYSQL_GROUP_REPLICATION_HOSTGROUPS);
+	queue = wqueue<MySQL_Connection *>();
 	MyHostGroups=new PtrArray();
 	incoming_replication_hostgroups=NULL;
 	incoming_group_replication_hostgroups=NULL;

lib/MySQL_PreparedStatement.cpp

@@ -532,16 +532,18 @@ void MySQL_STMT_Manager_v14::ref_count_client(uint64_t _stmt_id ,int _v, bool lo
 						continue; // nothing left to clean up
 					}
 					MySQL_STMT_Global_info *a = it->second;
-					if (__sync_add_and_fetch(&a->ref_count_client, 0) == 0) {
+					if ((__sync_add_and_fetch(&a->ref_count_client, 0) == 0) &&
+						(a->ref_count_server == 0) ) // this to avoid that IDs are incorrectly reused
+					{
 						uint64_t hash = a->hash;
 						auto s2 = map_stmt_hash_to_info.find(hash);
 						if (s2 != map_stmt_hash_to_info.end()) {
 							map_stmt_hash_to_info.erase(s2);
 						}
 						__sync_sub_and_fetch(&num_stmt_with_ref_client_count_zero,1);
-						if (a->ref_count_server == 0) {
+						//if (a->ref_count_server == 0) {
 							//__sync_sub_and_fetch(&num_stmt_with_ref_server_count_zero,1);
-						}
+						//}
 						// m.erase(it);
 						// delete a;
 						i++;

lib/MySQL_Session.cpp

@@ -2906,6 +2906,13 @@ handler_again:
 										sprintf(sqlstate,"%s",mysql_sqlstate(myconn->mysql));
 										client_myds->myprot.generate_pkt_ERR(true,NULL,NULL,client_myds->pkt_sid+1,mysql_errno(myconn->mysql),sqlstate,(char *)mysql_stmt_error(myconn->query.stmt));
 										client_myds->pkt_sid++;
+										if (previous_status.size()) {
+											// an STMT_PREPARE failed
+											// we have a previous status, probably STMT_EXECUTE,
+											//    but returning to that status is not safe after STMT_PREPARE failed
+											// for this reason we exit immediately
+											wrong_pass=true;
+										}
 									}
 									break;
 								case PROCESSING_STMT_EXECUTE: