MiniAccumuloClusterControl.stop(ServerType server, String hostname) does nothing with hostname

**Describe the bug**
Calling the method will stop all servers of the type

**Versions (OS, Maven, Java, and others, as appropriate):**
- Affected version(s) of this project: 2.0+

Locate the implementation of MiniAccumuloClusterControl.stop(ServerType server, String hostname) and read how server selection is handled. Check existing tests for MiniAccumuloClusterControl, then verify that stopping with a hostname affects only the matching server rather than every server of that type.

Written by the indexing model from the issue text.