Rename xdc_rdoc_manager record field.
Rename xdc_rdoc_manager record field.

From ddoc_replicator to rdoc_replicator. Because it replicates
replication documents, not design documents.

Change-Id: I4158cb6f7de0f23da7d24663ac7b7b0f4fbf194b
Reviewed-on: http://review.couchbase.org/48027
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

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