recipetool: Fix list concatenation when using edit

If there are multiple appends, ensure we concatenate compatible things:

Traceback (most recent call last):
  File "/home/akiernan/poky/scripts/recipetool", line 111, in <module>
    ret = main()
  File "/home/akiernan/poky/scripts/recipetool", line 100, in main
    ret = args.func(args)
  File "/home/akiernan/poky/scripts/lib/recipetool/edit.py", line 38, in edit
    return scriptutils.run_editor([recipe_path] + appends, logger)
TypeError: can only concatenate list (not "tuple") to list

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>