Include pid in per process stat names.
Include pid in per process stat names.

So that if we have several processes with the same name, it's easier
to distinguish them. It also simplifies the logic a bit.

Change-Id: I1cecaad40a281c57d4a8b6da902f2430c5939301
Reviewed-on: http://review.couchbase.org/46914
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

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