Add usage/help message to so-monitor-add

salt/common/tools/sbin/so-monitor-add

@@ -2,4 +2,22 @@
 
 . /usr/sbin/so-common
 
+usage() {
+  read -r -d '' message <<- EOM
+		usage: so-monitor-add [-h] NIC
+
+    positional arguments:
+      NIC           The interface you want to add to the monitor bond
+
+    optional arguments:
+      -h, --help    Show this help message and exit
+	EOM
+  echo "$message"
+  exit 1
+}
+
+if [[ $# -eq 0 || $# -gt 1 ]] || [[ $1 == '-h' || $1 == '--help' ]]; then
+  usage
+fi
+
 add_interface_bond0 "$1"