Reduce the number of nodes for Linux

I'm running out of filedescriptors on my Ubuntu box
(without any tuning set up). I guess most other people
using it will encounter the same problem so lets just
reduce the number of nodes and vbuckets used in the
test for Linux.

Change-Id: I4cdb571d838945046e362ac0cd4cd7d4f813b20b
Reviewed-on: http://review.couchbase.org/27933
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>