Clean up printf() argument list.

Splitting %s from \n makes it clearer that the %s's in question take
arguments that already include a newline, and that the subsequent \n
adds a blank line.

Change-Id: I5bac8ca80b42f7de980ad29480042cae3166ff7e
Reviewed-on: https://code.wireshark.org/review/2797
Reviewed-by: Guy Harris <guy@alum.mit.edu>