Requests an indexer to be deleted and waits until it is deleted.

Deleting an indexer is an asynchronous process, it is equivalent to running:

 hbase-indexer update-indexer -n indexer-name --lifecycle DELETE_REQUESTED

HBase Indexer will react to this by performing some cleanup and then
really deleting the indexer definition. The cleanup involves, among other
things, deleting the SEP subscription (= the HBase replication peer).

Running indexer processes will also be stopped ASAP, though not guaranteed
to be done before this tool returns (which would involve polling all
servers in the cluster).
