Ignore index size in Engine.DiskSize().
Ignore index size in Engine.DiskSize().

TSM includes index in DiskSize(), however, indexes are not copied
and shouldn't be included in this method. This causes issues with
`copy-shard`.

nooproblem/influxdb,nooproblem/influxdb,influxdata/influxdb,nooproblem/influxdb,linearb/influxdb,nooproblem/influxdb,li-ang/influxdb,influxdata/influxdb,influxdb/influxdb,influxdb/influxdb,mark-rushakoff/influxdb,mark-rushakoff/influxdb,linearb/influxdb,linearb/influxdb,influxdb/influxdb,linearb/influxdb,linearb/influxdb,li-ang/influxdb,influxdb/influxdb,mark-rushakoff/influxdb,influxdb/influxdb,mark-rushakoff/influxdb,mark-rushakoff/influxdb,mark-rushakoff/influxdb,influxdb/influxdb,nooproblem/influxdb