Bug#16143 mysql_stmt_sqlstate returns an empty string instead of '00000'

- Init sql_state in mysql_stmt_init


libmysql/libmysql.c:
  Init sql_state to not_error_sql_state in mysql_init
tests/mysql_client_test.c:
  Add test for mysql_stmt_sqlstate after mysql_stmt_init

libmysql/libmysql.c

@@ -2008,6 +2008,7 @@ mysql_stmt_init(MYSQL *mysql)
   stmt->mysql= mysql;
   stmt->read_row_func= stmt_read_row_no_result_set;
   stmt->prefetch_rows= DEFAULT_PREFETCH_ROWS;
+  strmov(stmt->sqlstate, not_error_sqlstate);
   /* The rest of statement members was bzeroed inside malloc */
 
   DBUG_RETURN(stmt);