Don't segfault in r_io_shutdown_client_fd() if there's no fdholder for the given fd.
Don't segfault in r_io_shutdown_client_fd() if there's no fdholder for the given fd.

svartika/ccnx,cawka/ndnx,cawka/ndnx,svartika/ccnx,svartika/ccnx,cawka/ndnx,svartika/ccnx,cawka/ndnx,svartika/ccnx,svartika/ccnx,ebollens/ccnmp,svartika/ccnx,ebollens/ccnmp,cawka/ndnx,ebollens/ccnmp,ebollens/ccnmp