JSCBC-465: Enable threshold logging by default.
JSCBC-465: Enable threshold logging by default.

Motivation
----------
The minor version bumps related to the upcoming server
release are intended to perform threshold logging by
default.

Changes
-------
Pass the threshold logging enablement flag to libcouchbase
via the connection string by default.

Change-Id: I515999ada0d63ed48ecd6d399b4c6d727f31eac3
Reviewed-on: http://review.couchbase.org/93210
Reviewed-by: Mike Goldsmith <c43a3c67d7a1203c37ce25b098df0254011e1ce6@gmail.com>
Tested-by: Brett Lawson <c8c4369773d7d7226e031f0c4af62e3f38a08510@gmail.com>

couchbase/couchnode,brett19/couchnode,couchbase/couchnode,couchbase/couchnode,brett19/couchnode,brett19/couchnode,couchbase/couchnode