The database has a mechanism of performing internal CQL queries,
mainly to edit its own local tables. Unfortunately, it's easy
to use the interface incorrectly - e.g. issuing an `ALTER TABLE`
statement on a non-local table will result in not propagating
the schema change to other nodes, which in turn leads to
inconsistencies. In order to avoid such mistakes (one of them
was a root cause of #6513), when an attempt to alter a distributed
table via a local interface is performed, it results in an error.
Tests: unit(dev)
Fixes#6700
Message-Id: <61be3defb57be79f486e6067ceff4f4c965e34cb.1592990796.git.sarna@scylladb.com>
835734c99d