Change memory measurement from gb to kb for better resolution.
The existing memory measurement like 2.3g is now changed to 2379404 kb.
This is for better comparison of memory usage among tests

Change-Id: I27a0f1e85e718d436328d0d5c8621d65964185c9
Reviewed-on: http://review.couchbase.org/37050
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Li Yang <lichenyang2@gmail.com>