"
This miniseries ensures that system tables are not checked
for having view updates, because they never do.
What's more, distributed system table is used in the process,
so it's unsafe to query the table while streaming it.
Tests: unit (release), dtest(update_cluster_layout_tests.py:TestUpdateClusterLayout.simple_decommission_node_2_test)
"
* 'fix_checking_if_system_tables_need_view_updates_3' of https://github.com/psarna/scylla:
streaming: don't check view building of system tables
database: add is_internal_keyspace
streaming: remove unused sstable_is_staging bool class
(cherry picked from commit d09d4bbd91)
b72a94b53e