When a node changes its IP we need to store the mapping in
system.peers and update token_metadata.topology and erm
in-memory data structures.
The test_change_ip was improved to verify this new
behaviour. Before this patch the test didn't check
that IPs used for data requests are updated on
IP change. In this commit we add the read/write check.
It fails on insert with 'node unavailable'
error without the fix.
6e7bbc94f4