And move-assign to _pending_ranges_interval_map[keyspace_name]
only when done.
This is more effient since there's no need to look up
_pending_ranges_interval_map[keyspace_name] for every insert to the
interval_map.
And it is exception safe in case we run out of memory mid-way.
Refs #7220
Test: unit(dev)
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20200916115059.788606-1-bhalevy@scylladb.com>
f207cff73d