clamonacc: Enable fanotify prevention in OnAccessMountPath

[xlejo]

This changes the behavior of OnAccessMountPath with OnAccessPrevention.

• If prevention is enabled, all paths in OnAccessMountPath will be enabled excluding the root directory and non-mountpoints!

Config and behavior example:

OnAccessExcludeRootUID yes
OnAccessExcludeUname clamav
OnAccessPrevention yes
OnAccessMountPath /media/user/drive        # prevention is enabled
OnAccessMountPath /                        # prevention is disabled for root directory
OnAccessMountPath /media/user2/other-drive # prevention is enabled
OnAccessMountPath /media                   # prevention is disabled for non-mountpoints

This would be very useful for real-time analysis (and prevention) of media drives.