MB-10304 upr client: add list_streams() and remove_stream() API

1. list_streams(Pid)
Returns a list for partitions for which active streams exist.

2. remove_stream(Pid, PartId)
If an active stream for this parititon already exist, request
server to close the stream.

Change-Id: I56d3a1bab45b921e7ad15cc2d127f357d2a1ea7b
Reviewed-on: http://review.couchbase.org/33986
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>