So far this only prevented the creation of the toplevel
directory. This does not cover all problem cases,
particularly when said directory is supposed to be a mount
point, including NFS and glusterfs beside ZFS.
The directory based storages we have already use mkpath
whenever they need to create files, and for actions on files
which are supposed to exist it's fine if it errors out.
So it should also be safe to skip the creation of standard
subdirectories in activate_storage().
Additionally NFS and glusterfs storages should also accept
the mkdir option as they otherwise may exhibit similar
issues, eg. when an NFS storage is mounted onto a directory
inside a ZFS subvolume.
The parse_proc_mounts change made the glusterfs is_mounted
check fail (causing it to be shown as inactive on the GUI).
The NFS check was stricter (not allowing a trailing / in the
source anymore).
This makes no sense because it should always be exclusive.
Also RDB checks it self.
LVM has not possibility to use lvchange.
DRBD is this feature not implemented.
