New csf v6.21

Changes:

• Modified auto-update logic to only create the /etc/cron.d/csf_update file if it does not already exist
• Fix permissions on csf man file and directory
• Modified webmin module paths to be relative rather than absolute so that webmin via mod_proxy works correctly
• Fixed “in” direction –tempallow/–tempdeny leaking into [comment]
• Added nginx regex for ModSecurity rule detection. Remember to set MODSEC_LOG correctly for the location of the nginx error log
• Fixed file permission/ownership problem on DirectAdmin servers for the /plugins directory