[PATCH] support/shell-container.c: Use support_copy_file_range

[DJ Delorie]

fweimer@redhat.com (Florian Weimer) writes:
> 	* support/shell-container.c (copy_func): Call
> 	support_copy_file_range instead of copy_file_range to support
> 	cross-device copies.

I'm kinda surprised HJ didn't do this when he added
support_copy_file_range itself, since this is WHY we added that.
Regardless, LGTM.

Reviewed-by: DJ Delorie <dj@redhat.com>