MB-10171: added capturing of master vbucket _local docs to /diag

Particularly so that we can see xdcr checkpoints.

Change-Id: I658852aa3587541527684049529f4e0c9ee35447
Reviewed-on: http://review.couchbase.org/34028
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
bp:MB-100 use sockets pool for long blocking memcached calls

so far it is just wait_for_checkpoint_persistence but there
will be more of them

Change-Id: Iaeca8739de6358e2309d07c04d2a9a18dca63be6
Orig-Reviewed-on: http://review.couchbase.org/32748
Reviewed-on: http://review.couchbase.org/34029
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
bp:MB-100 allow free form Destination in ns_connection_pool

there's no need to require it to be {Host, Port, Ssl}

Change-Id: Icee603aeab20a5199a640abb2c2ce89dd00b6a8b
Orig-Reviewed-on: http://review.couchbase.org/32747
Reviewed-on: http://review.couchbase.org/34030
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
bp:MB-100 dialyzer fix

Change-Id: Id738748957f12da4accd5a03174dfb18d3531f53
Orig-Reviewed-on: http://review.couchbase.org/32828
Reviewed-on: http://review.couchbase.org/34031
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>