Try to fix memory leak on redis stat
Try to fix memory leak on redis stat

Issue: #500
Reported by: @mozzan

andrejzverev/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,andrejzverev/rspamd,AlexeySa/rspamd