ensure calling mysql_server_end() when releasing the mysql storage module

from mysql.h :
    mysql_server_init/end need to be called when using libmysqld or
    libmysqlclient (exactly, mysql_server_init() is called by mysql_init() so
    you don't need to call it explicitely; but you need to call
    mysql_server_end() to free memory). The names are a bit misleading
    (mysql_SERVER* to be used when using libmysqlCLIENT). So we add more general
    names which suit well whether you're using libmysqld or libmysqlclient. We
    intend to promote these aliases over the mysql_server* ones.