import tool is too brittle (fails on existing role)

Fails for me with Caught exception org.apache.hadoop.hive.metastore.api.InvalidObjectException with message <Role admin already exists>

Not sure what to do with this now... someone might have run the import before, but that didn't finish because I don't see anything non-default in Hbase metastore tables. Or maybe role admin exists by default.

There should be a better way to handle this ("clear" flag? confirmation if something already exists?)