backport: don't crash stats collector encountering long stat name
backport: don't crash stats collector encountering long stat name

Change-Id: Ic91f62ee9248cf69ad7510a265d2a13ee7344947
Orig-Reviewed-on: http://review.couchbase.org/7072
Reviewed-on: http://review.couchbase.org/13147
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

nimishzynga/ns_server,vzasade/ns_server,membase/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,pavel-blagodov/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server,membase/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,t3rm1n4l/ns_server,t3rm1n4l/ns_server,daverigby/ns_server,ceejatec/ns_server,nimishzynga/ns_server,ceejatec/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,daverigby/ns_server,daverigby/ns_server,membase/ns_server,vzasade/ns_server,mschoch/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,daverigby/ns_server,vzasade/ns_server,membase/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,mschoch/ns_server,ceejatec/ns_server