MB-10502: adjust vbucket-seqno stats and unbreak xdcr
MB-10502: adjust vbucket-seqno stats and unbreak xdcr

New-style checkpointing is using this stat and recent ep-engine change
requires different stat name.

Change-Id: Idc5674359ab2999f8afa907910765d9d6267e379
Reviewed-on: http://review.couchbase.org/34668
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

daverigby/ns_server,t3rm1n4l/ns_server,membase/ns_server,mschoch/ns_server,membase/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,mschoch/ns_server,ceejatec/ns_server,mschoch/ns_server,mschoch/ns_server,nimishzynga/ns_server,mschoch/ns_server,daverigby/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server