Fix spelling mistake in constants.py

Of course instance creation don't have any modem, and the comment was just
talking about modes. Sorry to everybody expecting whistles.

Reviewed-by: imsnah

lib/constants.py

@@ -116,7 +116,7 @@ REPLACE_DISK_PRI = "replace_primary"
 REPLACE_DISK_SEC = "replace_secondary"
 REPLACE_DISK_ALL = "replace_all"
 
-# instance creation modem
+# instance creation modes
 INSTANCE_CREATE = "create"
 INSTANCE_IMPORT = "import"