`mc rm` fails to delete files

[kubajecminek]

When using mc client, I'm unable to delete the files due to missing Last-Modified header.

$ mc rm zs3/my-bucket/README.md
mc: <ERROR> Failed to remove `zs3/my-bucket/README.md`. Last-Modified time format is invalid, failed with unable to parse  in any of the input formats: [Mon, 2 Jan 2006 15:04:05 GMT Mon, _2 Jan 2006 15:04:05 GMT Mon, _2 Jan 06 15:04:05 GMT]

Even though setting Last-Modified in handleHeadObject handler is enough, it would be nice to add it to other handlers as well, because then mc would be able to display it instead of:

$ mc ls zs3/my-bucket
[0001-01-01 00:57:44 LMT] 6.1KiB STANDARD README.md

Thanks for zs3.