10592 misc. metaslab and vdev related ZoL bug fixes
Portions contributed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Giuseppe Di Natale <guss80@gmail.com>
Reviewed by: George Melikov <mail@gmelikov.ru>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Tony Hutter <hutter2@llnl.gov>
Reviewed by: Kody Kantor <kody.kantor@joyent.com>
Approved by: Dan McDonald <danmcd@joyent.com>

@@ -109,13 +109,13 @@
              If the -q option is also specified, don't print the labels.
 
              If the -u option is also specified, also display the uberblocks
              on this device.
 
-     -L      Disable leak tracing and the loading of space maps.  By default,
-             zdb verifies that all non-free blocks are referenced, which can
-             be very expensive.
+     -L      Disable leak detection and the loading of space maps.  By
+             default, zdb verifies that all non-free blocks are referenced,
+             which can be very expensive.
 
      -m      Display the offset, spacemap, and free space of each metaslab.
 
      -mm     Also display information about the on-disk free space histogram
              associated with each metaslab.