[TEST] RecoveryWhileunderLoadTests sometimes need higher timeouts

In some cases when we have a lot of docs with lots of shards
recovery takes longer than 1m causing the tests to fail before all
shards are recovered. This commit raises the timeout in this test to
5m max while it's rarely needed.

This commit also adds an assertion to ElasticsearchAssertions that
ensures that the cluster health requests are not hitting a timeout.