libzfs_core: lzc_destroy and lzc_get_prop

[baloo]

For docker to implement zfs (https://github.com/docker/docker/pull/7901) I'd like to have two api in the libzfs_core:

• lzc_destroy, to destroy a filesystem (IOCTL ZFS_IOC_DESTROY)
• lzc_get_prop, to read property from a filesystem

I'm unsure how a get_prop does not conflict with the original libzfs_core goals (http://blog.delphix.com/matt/files/2012/01/The_Future_of_LibZFS.pdf).

[maci0]

+1