Includes configure changes and Jenkins setting change.

Noticed mem3_sync_event_listner tests still fails intermetently, add a debug
log to it to hopefully find the cause of the failure.

Previously any failed node or rexi worker error resulted in requests failing
immediately even though there were available workers to keep handling the
request. This was because the progress check function didn't account for the
fact that partition requests only use a handful of shards which, by design, do
not complete the full ring.

Here we fix both partition info queries and dreyfus search functionality. We
follow the pattern from fabric and pass through a set of "ring options" that
let the progress function know it is dealing with partitions instead of a full
ring.

Adjust way to detect presence of hastings for Ken

After moving ken from https://github.com/apache/couchdb-ken to
https://github.com/apache/couchdb/tree/master/src/ken. The directory
structure related to ken is changed for downstream including Cloudant.
Increase more way to detect presence of hastings for Ken so that
Ken can work correctly for geospatial index.

Mango text indexes currently throw function clauses when queries in two
situations:

1) Empty Selector
2) Operators with empty arrays.

We fix this issue and change the behavior as follows:

1) Any empty selector will fall back on _all_docs (like json indexes).
2) $or, $and, $in, $all that specify an empty arrays
will be treated as no-op when combined with other operators.
3) A single no-nop query such as {"$or": []} will not be executed and
return nothing just like json indexes.
4) $nin with an empty array will return all docs that match the field,
just like json indexes.

Adds a new configuration field, `couch_httpd_auth.same_site` which
sets the `SameSite` attribute of the CouchDB auth cookie. If no
value is set (the default), no `SameSite` attribute is added.

Refs #2221