c70f321c6f added an extra check if KS
exists. This check can throw `data_dictionary::no_such_keyspace`
exception, which is supposed to be caught and a more user-friendly
exception should be thrown instead.
This commit fixes the above problem and adds a testcase to validate it
doesn't appear ever again.
Also, I moved the check for the keyspace outside of the `for` loop, as
it doesn't need to be checked repeatedly.
Fixes: scylladb/scylladb#20097Closesscylladb/scylladb#20404
60af48f5fd