FreeNAS Code

Remove fixed context.

add help_text for Remote ZFS filesystem

Fix zvol deletion with cascade=True and destroy=True so it doesn't traceback.

Clean up an unused import and fix a shadowed declaration.

Determine whether or not a path is owned by a mountpoint by using struct stat data returned by os.stat(..).

Remove unnecessary os imports since it's handled at the top of the module.

Rename volume_export to volume_detach to be more generic [1].
More 'renaming' needs to occur, but this will be an 8.2+ thing,
not an 8.0.3 thing (this is being done to avoid thrashing
dlavinge).

Mash zfs_export into volume_detach because it was only one
command.

Iterate through commands in a loop and stop at any errors to
ensure that things can be cleaned up at a later point in time
if something fails.

Document desired behavior and requirements.

1. Requested by jpaetzel.

Remove the try-except swallowing around volume 'exporting'.

try-except swallowing gets our software out of synch with reality.
It is also a really bad practice as it hides other potential bugs
with the code, and ultimately we should be fixing the issues, not
disguising bugs in our code.

Doing this also forces the sysadmin to deal with the issue ASAP
instead of causing head-scratching later on when things aren't
working as expected, as I've had to deal with over the
phone/IRC/etc with several users/customers.

One should always detach swaps when removing volumes, datasets, etc.

Initial work to get a list of volumes from a plugin started.

Do-Not-Merge: Plugin stuff stays out of TrueNAS

check whether there is a volume_name before validate for UFS