coredump: '% at the end' shouldn't bypass core_uses_pid logic

"goto end" should not bypass the "Backward compatibility with
core_uses_pid" code, move this label up.

While at it,

	- It is ugly to copy '|' into cn->corename and then inc
	  the pointer for argv_split().

	  Change format_corename() to increment pat_ptr instead.

	- Remove the dead "if (*pat_ptr == 0)" in format_corename(),
	  we already checked it is not zero.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Colin Walters <walters@verbum.org>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>