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>

arch/x86/ia32/ia32_aout.c

@@ -131,7 +131,7 @@ static int load_aout_binary(struct linux_binprm *bprm)
 		return -ENOMEM;
 
 	/* Flush all traces of the currently running executable */
-	retval = flush_old_exec(bprm);
+	retval = begin_new_exec(bprm);
 	if (retval)
 		return retval;