Do not use couchbase session store by default

Because it has to be configured separately from config/couchbase.yml
and people might forget to change hostname there for example

Change-Id: I9a229e22c3a842a73972d55ff0f98a1cfe2a16ff
Make version checks not so strict

Change-Id: I6dfe084d0997f14cde3ad78a7a1eea5b99c21c0f