OpenZFS 8959 - Add notifications when a scrub is paused or resumed

Authored by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed by: Alek Pinchuk <pinchuk.alek@gmail.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Gordon Ross <gwr@nexenta.com>
Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov>

Porting Notes:
- Brought #defines in eventdefs.h in line with ZFS on Linux format.
- Updated zfs-events.5 with the new events.

OpenZFS-issue: https://www.illumos.org/issues/8959
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/c862b93eea
Closes #7049

man/man5/zfs-events.5

@@ -328,7 +328,34 @@ Issued when a scrub is started on a pool.
 \fBscrub.finish\fR
 .ad
 .RS 12n
-Issued when a pool have finished scrubbing.
+Issued when a pool has finished scrubbing.
+.RE
+
+.sp
+.ne 2
+.na
+\fBscrub.abort\fR
+.ad
+.RS 12n
+Issued when a scrub is aborted on a pool.
+.RE
+
+.sp
+.ne 2
+.na
+\fBscrub.resume\fR
+.ad
+.RS 12n
+Issued when a scrub is resumed on a pool.
+.RE
+
+.sp
+.ne 2
+.na
+\fBscrub.paused\fR
+.ad
+.RS 12n
+Issued when a scrub is paused on a pool.
 .RE
 
 .sp