* TestClusters: Convert the security plugin
This PR moves security tests to use TestClusters.
The TLS test required support in testclusters itself, so the correct
wait condition is configgured based on the cluster settings.
* PR review
This adds a new security/qa test for TLS on a basic license.
It starts a 2 node cluster with a basic license, and TLS enabled
on both HTTP and Transport, and verifies the license type, x-pack
SSL usage and SSL certificates API.
It also upgrades the cluster to a trial license and performs that
same set of checks (to ensure that clusters with basic license
and TLS enabled can be upgraded to a higher feature license)
Backport of: #40714
Alpar Torok
Mark Vieira
Tim Vernum