Add scrub after resilver zed script

* Add a zed script to kick off a scrub after a resilver.  The script is
disabled by default.

* Add a optional $PATH (-P) option to zed to allow it to use a custom
$PATH for its zedlets.  This is needed when you're running zed under
the ZTS in a local workspace.

* Update test scripts to not copy in all-debug.sh and all-syslog.sh by
default.  They can be optionally copied in as part of zed_setup().
These scripts slow down zed considerably under heavy events loads and
can cause events to be dropped or their delivery delayed. This was
causing some sporadic failures in the 'fault' tests.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #4662 
Closes #7086

man/man8/zed.8.in

@@ -27,6 +27,7 @@ ZED \- ZFS Event Daemon
 [\fB\-L\fR]
 [\fB\-M\fR]
 [\fB\-p\fR \fIpidfile\fR]
+[\fB\-P\fR \fIpath\fR]
 [\fB\-s\fR \fIstatefile\fR]
 [\fB\-v\fR]
 [\fB\-V\fR]
@@ -78,9 +79,16 @@ Read the enabled ZEDLETs from the specified directory.
 .BI \-p\  pidfile
 Write the daemon's process ID to the specified file.
 .TP
+.BI \-P\  path
+Custom $PATH for zedlets to use.  Normally zedlets run in a locked-down
+environment, with hardcoded paths to the ZFS commands ($ZFS, $ZPOOL, $ZED, ...),
+and a hardcoded $PATH.  This is done for security reasons.  However, the
+ZFS test suite uses a custom PATH for its ZFS commands, and passes it to zed
+with -P.  In short, -P is only to be used by the ZFS test suite; never use
+it in production!
+.TP
 .BI \-s\  statefile
 Write the daemon's state to the specified file.
-
 .SH ZEVENTS
 .PP
 A zevent is comprised of a list of nvpairs (name/value pairs).  Each zevent