Add GET LBA STATUS command support to CTL.

It is implemented for LUNs backed by ZVOLs in "dev" mode and files.
GEOM has no such API, so for LUNs backed by raw devices all LBAs will
be reported as mapped/unknown.

MFC after:	2 weeks
Sponsored by:	iXsystems, Inc.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275474 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f