MB-8281: send storage totals with bucket info

We need to synchronize cluster_storage_info and
last_bucket_stats because their values are used
on the UI at moment when bucket details section
is open. Now to get stats last_bucket_stats uses
ns_doctor as like cluster_storage_info.

This commit also makes sure that we send basicStats _only_ if UI
explicitly asks for it.

Change-Id: I5aaba4706fb425a16c62285e0b9539bbcde7bfde
[alk@tut.by: fixed backwards compat issue with interesting_stats]
[alk@tut.by: improved commit message]
Signed-off-by: Aliaksey Kandratsenka <alk@tut.by>
Reviewed-on: http://review.couchbase.org/27495
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>