zpool iostat/status -c improvements

Users can now provide their own scripts to be run
with 'zpool iostat/status -c'. User scripts should be
placed in ~/.zpool.d to be included in zpool's
default search path.

Provide a script which can be used with
'zpool iostat|status -c' that will return the type of
device (hdd, sdd, file).

Provide a script to get various values from smartctl
when using 'zpool iostat/status -c'.

Allow users to define the ZPOOL_SCRIPTS_PATH
environment variable which can be used to override
the default 'zpool iostat/status -c' search path.

Allow the ZPOOL_SCRIPTS_ENABLED environment
variable to enable or disable 'zpool status/iostat -c'
functionality.

Use the new smart script to provide the serial command.

Install /etc/sudoers.d/zfs file which contains the sudoer
rule for smartctl as a sample.

Allow 'zpool iostat/status -c' tests to run in tree.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #6121 
Closes #6153

cmd/zpool/Makefile.am

@@ -36,12 +36,31 @@ dist_zpoolexec_SCRIPTS = \
 	zpool.d/label \
 	zpool.d/locate_led \
 	zpool.d/lsblk \
+	zpool.d/media \
 	zpool.d/model \
 	zpool.d/serial \
 	zpool.d/ses \
 	zpool.d/size \
 	zpool.d/slaves \
 	zpool.d/slot \
+	zpool.d/smart \
+	zpool.d/smartx \
+	zpool.d/temp \
+	zpool.d/health \
+	zpool.d/r_proc \
+	zpool.d/w_proc \
+	zpool.d/r_ucor \
+	zpool.d/w_ucor \
+	zpool.d/nonmed \
+	zpool.d/defect \
+	zpool.d/hours_on \
+	zpool.d/realloc \
+	zpool.d/rep_ucor \
+	zpool.d/cmd_to \
+	zpool.d/pend_sec \
+	zpool.d/off_ucor \
+	zpool.d/ata_err \
+	zpool.d/pwr_cyc \
 	zpool.d/upath \
 	zpool.d/vendor
 
@@ -55,12 +74,31 @@ zpoolconfdefaults = \
 	label \
 	locate_led \
 	lsblk \
+	media \
 	model \
 	serial \
 	ses \
 	size \
 	slaves \
 	slot \
+	smart \
+	smartx \
+	temp \
+	health \
+	r_proc \
+	w_proc \
+	r_ucor \
+	w_ucor \
+	nonmed \
+	defect \
+	hours_on \
+	realloc \
+	rep_ucor \
+	cmd_to \
+	pend_sec \
+	off_ucor \
+	ata_err \
+	pwr_cyc \
 	upath \
 	vendor