unbreak delta recovery when there are non-kv nodes
unbreak delta recovery when there are non-kv nodes

Specifically, when we try to build delta recovery maps we shouldn't
consider non-kv nodes. Because if we do, delta recovery will obviously
fail.

Change-Id: Ic31ac6a57eac406575a8d509d04b72cb3fa0ebcb
Reviewed-on: http://review.couchbase.org/45101
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,ceejatec/ns_server,mschoch/ns_server,membase/ns_server,ceejatec/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,membase/ns_server,nimishzynga/ns_server,membase/ns_server