HPCC-8564 Added override settings for nproc to limits.conf

Added a soft of 4096 and hard of 8192 which matchs the default
kernel set values on ubuntu and centos 5.x.

Signed-off-by: Philip Schwartz <philip.schwartz@lexisnexis.com>
Merge pull request #3983 from pschwartz/HPCC-8564-nproc-override

HPCC-8564 Added override settigns for nproc to limits.conf

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>