exec: Rename flush_old_exec begin_new_exec

There is and has been for a very long time been a lot more going on in
flush_old_exec than just flushing the old state.  After the movement
of code from setup_new_exec there is a whole lot more going on than
just flushing the old executables state.

Rename flush_old_exec to begin_new_exec to more accurately reflect
what this function does.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 2528789..9b82bc1 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -534,7 +534,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 
 	/* Flush all traces of the currently running executable */
 	if (id == 0) {
-		ret = flush_old_exec(bprm);
+		ret = begin_new_exec(bprm);
 		if (ret)
 			goto err;