ip: return correct exit code on route failure

If kernel complains about ip route request, exit status should be
2 not 1.

This fixes regression introduced by:
commit 42ecedd4bae534fc688194a795eb4548c6530cda
Author: Roopa Prabhu <roopa@cumulusnetworks.com>
Date:   Tue Mar 17 19:26:32 2015 -0700

    fix ip -force -batch to continue on errors
1 file changed