init script doesn't check for corefile limits when starting

Customer installed DP3 on a system with /etc/security/limits.conf originally set to:

• soft core 0
• hard core 0

The Couchbase service started properly, but memcached refused to start with message:
'ns_1@.....' exited with status 71. Restarting. Messages: failed to ensure corefile creation

After setting /etc/security/limits.conf to:
couchbase hard nofile 10240
couchbase hard core unlimited

The server was able to start properly.

We need to check this before service start so that memcached doesn't continuously restart itself.