umount: only root can use "--types" option

System information

Type	Version/Name
Distribution Name	Ubuntu
Distribution Version	bionic (18.04.2)
Linux Kernel	4.15.0-46-generic
Architecture	x86_64
ZFS Version	0.7.5-1ubuntu16
SPL Version	0.7.5-1ubuntu1

Describe the problem you're observing

When I try to create a volume as a non root user, I get a pretty warning explaining that as a non root user zfs can't mount the volume. When I try to destroy a volume as a non root user, I get a technical warning (from /bin/umount)

The equivalent error can be seen here:

$ /bin/umount x --types foo
umount: only root can use "--types" option

Ideally, just as zfs create gives a human readable warning when it knows it can't mount a volume, zfs destroy should give a human readable warning when it knows it can't unmount a volume.

Describe how to reproduce the problem

$ sudo zfs allow user create,mount,destroy pool/vol
$ zfs create pool/vol/test
filesystem successfully created, but it may only be mounted by root
$ sudo zfs mount pool/vol/test
$ zfs destroy pool/vol/test
umount: only root can use "--types" option
cannot unmount '/vol/test': umount failed

Include any warning/errors/backtraces from the system logs