Add zfs.sh -r flag to reload modules

zfs.sh already can load and unload, so why not both?

This is convenient when developing changes to the module and you want
to rapidly make some changes, rebuild the module, reload the module,
and test the changes.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #12450

scripts/zfs.sh

@@ -14,6 +14,7 @@ fi
 PROG=zfs.sh
 VERBOSE="no"
 UNLOAD="no"
+LOAD="yes"
 STACK_TRACER="no"
 
 ZED_PIDFILE=${ZED_PIDFILE:-/var/run/zed.pid}
@@ -44,12 +45,13 @@ DESCRIPTION:
 OPTIONS:
 	-h      Show this message
 	-v      Verbose
+	-r	Reload modules
 	-u      Unload modules
 	-S      Enable kernel stack tracer
 EOF
 }
 
-while getopts 'hvuS' OPTION; do
+while getopts 'hvruS' OPTION; do
 	case $OPTION in
 	h)
 		usage
@@ -58,8 +60,13 @@ while getopts 'hvuS' OPTION; do
 	v)
 		VERBOSE="yes"
 		;;
+	r)
+		UNLOAD="yes"
+		LOAD="yes"
+		;;
 	u)
 		UNLOAD="yes"
+		LOAD="no"
 		;;
 	S)
 		STACK_TRACER="yes"
@@ -262,7 +269,8 @@ if [ "$UNLOAD" = "yes" ]; then
 	           unload_modules_linux
 		   ;;
 	esac
-else
+fi
+if [ "$LOAD" = "yes" ]; then
 	case $UNAME in
 		FreeBSD)
 		   load_modules_freebsd