If cluster health times out don't index lots of documents

The SearchWithRandomExceptionTests aim to catch problems when resources
are not closed due to exceptions etc. Yet in some cases the random seeds
cause the index to never be fully allocated so we basically go into a
ping-pong state where we try to allocate shards back and forth on nodes.
This causes all docs to time out which in-turn causes the tests to run
for a very long time (hours or days).
If we can not allocate the index and get to a yellow state we simply
index only one doc and expected all searches to fail.

This commit also beefs up the assertions in this test to check if
documents are actually present if they are indexed and refresh was
successful.

Closes #3694