qemuMonitorJSONGetAllBlockStatsInfo: Directly probe data from 'query-named-block...

qemuMonitorJSONGetAllBlockStatsInfo: Directly probe data from 'query-named-block-nodes'

Currently the data which was probed for statistics from
'query-named-block-nodes' was updated in a separate call in
qemuMonitorJSONBlockStatsUpdateCapacityBlockdev.

This patch moves and adapts the code so that everything is probed in
qemuMonitorJSONGetAllBlockStatsInfo.

qemuMonitorJSONBlockStatsUpdateCapacityBlockdev is now an empty function
and will be removed later.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>