krb5_child: Fix use after free in debug message
debug_prg_name is used in debug_fn and it was allocated under
talloc context "kr". The variable "kr" was removed before the last debug
messages in function main. It is very little change that it will be overridden.
It is possible to see this issue with exported environment variable
TALLOC_FREE_FILL=255
Reviewed-by: Sumit Bose <sbose@redhat.com>