The implementation of get_range_to_address_map has a default behaviour,
when getting an empty keypsace, it uses the first non-system keyspace
(first here is basically, just a keyspace).
The current implementation has two issues, first, it uses a reference to
a string that is held on a stack of another function. In other word,
there's a use after free that is not clear why we never hit.
The second, it calls get_non_system_keyspaces twice. Though this is not
a bug, it's redundant (get_non_system_keyspaces uses a loop, so calling
that function does have a cost).
This patch solves both issues, by chaning the implementation to hold a
string instead of a reference to a string.
Second, it stores the results from get_non_system_keyspaces and reuse
them it's more efficient and holds the returned values on the local
stack.
Fixes#6465
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
(cherry picked from commit 69a46d4179)