api::set_storage_service(): fix the 'nodetool enablebackup' API
api::set_storage_service(): fix the 'nodetool enablebackup' API

'nodetool enable/disablebackup' callback was modifying only the
existing keyspaces and column families configurations.
However new keyspaces/column families were using
the original 'incremental_backups' configuration value which could
be different from the value configured by 'nodetool enable/disablebackup'
user command.

This patch updates the database::_enable_incremental_backups per-shard
value in addition to updating the existing keyspaces and column families
configurations.

Fixes #845

Signed-off-by: Vlad Zolotarov <976c0f8d0852ed6439ad273880b400a75a7c41d0@cloudius-systems.com>

kjniemi/scylla,raphaelsc/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,raphaelsc/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,kjniemi/scylla,scylladb/scylla,scylladb/scylla,raphaelsc/scylla,duarten/scylla,avikivity/scylla,kjniemi/scylla