Fix argcompletion shell code generation

Regression introduced by c37cd68,
which bumped argcompletion, which included an undocumented breaking
change (kislyuk/argcomplete#246) that lead to
generating `d m a k e` instead of `dmake` in the final bash script,
breaking the completion (and maybe other things).

dmake/cli.py

@@ -22,7 +22,7 @@ def add_argument(parsers, *args, **kwargs):
 
 
 def completion_action(args):
-    print(argcomplete.shellcode('dmake', shell=args.shell))
+    print(argcomplete.shellcode(['dmake'], shell=args.shell))
 
 
 # Find root