radosgw: increase nofiles ulimit on sysvinit machines

Clusters with many OSDs require a higher nofiles ulimit than the RHEL default. Increase it.

Tested-by: Dan van der Ster <daniel.vanderster@cern.ch>
Signed-off-by: Dan van der Ster <daniel.vanderster@cern.ch>
Merge pull request #934 from cernceph/wip-rgw-ulimit

radosgw: increase nofiles ulimit on sysvinit machines