Adjust ulimit on RPM platforms

The default number of processes/threads (ulimit -u) on rhel6 and clones
is 1024, which is too little for varnish.

This patch adds a variable NPROC to sysconfig/initscript suppport in the
rpm package. If no value is set in sysconfig, it will be set to 10000.
Revert "Adjust ulimit on RPM platforms"

Duplicate commit, already done by daghf in ebb667015cc531c2cdc11c709b67c09e75467275

This reverts commit bca2da56c94c0b472b667f0d1bcf2444d4ae6ff8.