Add check for mkisofs

This check helps to avoid exit the script with the message indicating
success even though the mkisofs is missing and an image has not been created.

contrib/create-basic-configdrive

@@ -55,6 +55,12 @@ if [ $(id -u) -eq 0 ]; then
     exit 1
 fi
 
+# mkisofs tool check
+if ! which mkisofs &>/dev/null; then
+    echo "$0: mkisofs tool is required to create image." >&2
+    exit 1
+fi
+
 if [ -z "$HNAME" ]; then
     echo "$0: The hostname parameter '-H' is required." >&2
     exit 1