Disable include_docs test for GCouchbase

The gevent api cannot cleanly use include_docs here; previously we
relied on the server to retrieve this, but the server no longer supports
this. Perhaps in some future time we can implement this within
libcouchbase itself, but until then, it's left unimplemented.

Change-Id: I1dc5cf86b4b063d251363f3d5fa14c8d29e8e6c1
Reviewed-on: http://review.couchbase.org/44149
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Volker Mische <volker.mische@gmail.com>