Simplify parameters handling for observe

* this static function is used only once
* almost all parameters used to output something
* it has generic name which says nothing about what the function does

Change-Id: I98836d70ecb047946fcf43efd782c127573caae1
Reviewed-on: http://review.couchbase.org/28071
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>