/opt/couchbase/bin/couchbase-server should warn if the ulimit is less than in the init.d script

For not root installs Couchbase server is launched via /bin/couchbase-server -- -noinput -detached. This script should warn if the open file descriptor limit is less than is specified in the init.d script. Currently it checks if ulimit is greater than 10240.

The couchbase-server script is not running as root and can't set the hard ulimit. It has historically simply warned if the limit is less than a given value; I propose for 3.1.2 we preserve that behavior.

http://src.couchbase.org/source/xref/3.1.0/ns_server/couchbase-server.sh.in#54

(With apologies to Patrick Varley, who's ticket I modified to put in 3.1.2. Patrick - if you still think we should try and raise the soft limit to 40960 and fail if we get an error in couchbase-server, then let's talk.)