PURGE BINARY LOGS should raise a warning if binary logging is disabled

If the server is started with skip-log-bin set, and if the user executes PURGE BINARY LOGS or RESET MASTER, then the server should warn the user that the statement will not work properly. The statement currently succeeds without raising any error or warning.

Steps to reproduce:

1. Add skip-log-bin to .cnf file
2. Restart database
3. run PURGE BINARY LOGS TO 'mysql-binlog.xxxx'; [or any other purge command like RESET MASTER, PURGE BINARY LOGS BEFORE etc]

Terminal output:
MariaDB [xxx_1]> PURGE BINARY LOGS BEFORE '2019-12-20 10:40:00';
Query OK, 0 rows affected (0.01 sec)