Default charset is not correct

There are two problems with charset:

1. For 2.3, the mariadb-c-connector version is v3.1.0, after v3.0.4 , mariadb-c-connector changed the default charset logical, the default charset will be latin1, so the function `mysql_get_character_set_info` will alway return latin1;
https://mariadb.com/kb/en/library/mariadb-connector-c-305-release-notes/
CONC-315: Change default character set to latin1

2. User can change the backend's charset setting, but using mysql_get_character_set_info will always get charset of monitor's connection;

Suggestion:
use query "select @@global.character_set_server"