zfs clone should not mount the clone if canmount == noauto

Creation of a new filesystem does not imply an intent to mount it.

Since canmount property is not inherited and its default value is 'on',
the only scenario where this matters is zfs clone -o canmount=noauto.
zfs create -o canmount=noauto already does not mount the new filesystem.

Also see:
https://www.illumos.org/issues/5984
https://reviews.csiden.org/r/228/
https://github.com/FransUrbo/zfs/commit/dd0e0e69f5b1c83bf2895ac00a0b83af77473175
https://github.com/zfsonlinux/zfs/issues/2241

Reviewed by: mahrens
MFC after: 8 days
Sponsored by: ClusterHQ