Add 409 index test
Add test to verify that index listing
Add delete, get, and 404 tests for index resource
Avoid race condition in index resource

* Use same ring for lifetime of request as ring could change
  mid-request (this could still be thwarted by calls which use the
  ring but don't take it as a parameter).

* For index to be considered existing it should exist both in the ring
  and in Solr.  This allows the 404 to kick in immediately after a
  delete rather than waiting seconds for Solr to cleanup.