fix a leak in replace_fd() users

replace_fd() began with "eats a reference, tries to insert into
descriptor table" semantics; at some point I'd switched it to
much saner current behaviour ("try to insert into descriptor
table, grabbing a new reference if inserted; caller should do
fput() in any case"), but forgot to update the callers.
Mea culpa...

[Spotted by Pavel Roskin, who has really weird system with pipe-fed
coredumps as part of what he considers a normal boot ;-)]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/coredump.c b/fs/coredump.c
index fd37fac..ce47379 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -450,11 +450,12 @@
 
 	cp->file = files[1];
 
-	replace_fd(0, files[0], 0);
+	err = replace_fd(0, files[0], 0);
+	fput(files[0]);
 	/* and disallow core files too */
 	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 
-	return 0;
+	return err;
 }
 
 void do_coredump(siginfo_t *siginfo, struct pt_regs *regs)