mount.zfs -q flag

This permits us to silence output from mount.zfs.

Signed-off-by: Richard Yao <ryao@gentoo.org>
GRSecurity 3.0 Compatibility: Use /sbin/mount.zfs instead of /bin/sh

Signed-off-by: Richard Yao <ryao@gentoo.org>
Don't go into userland to umount snapdir

Signed-off-by: Richard Yao <ryao@gentoo.org>