Code review comment for ~paul-meyer/cloud-init:fix-ntfs-mount

Just adding the comments we had during IRC discussion:

I'd prefer if we detected that we can't mount ntfs by checking for

a) is there an ntfs kernel module
b) is there a mount.ntfs tool in $PATH

vs. ignoring the error on certain distros;

The general worry is that the NTFS partition could have user-data on it; though I understand that for some distros which don't support NTFS that data wouldn't have come from instances running those distros.

It was also mentioned that images which don't support ntfs, could embed cloud-config, like:

"support_ntfs: false"

That could also be metadata that the AzureDatasource uses to determine if the mount failure is fatal or not.