MFC r324221:
MFV r316861: 6866 zdb -l should return non-zero if it fails to find any label
illumos/illumos-gate@64723e361134b2a2c45341334174f9d34002f8d0
https://github.com/illumos/illumos-gate/commit/64723e361134b2a2c45341334174f9d34002f8d0
https://www.illumos.org/issues/6866
Need this for #6865. To be generally more scripting-friendly, overload this issue with adding '-q' option which should skip printing any label information.
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Yuri Pankov <yuri.pankov@nexenta.com>