KUDU-3781: Add TLS support to MiniHms

This change adds the functionality of generating a PKCS12 keystore for
the MiniHms when TLS is enabled and wires the generated keystore into
the HMS configuration.

Added a very simple test for sanity checking, to confirm that the
HMS configs are properly generated, this should be replaced by a more
detailed test, when the HMS client TLS support is added.

Additionally, ExternalMiniClusterOptions and ExternalMiniCluster were
extended to support the added functionality.

Change-Id: I8fca647fd900fafc6d737c93a4af4565631839b7
Reviewed-on: http://gerrit.cloudera.org:8080/24374
Reviewed-by: Alexey Serbin <alexey@apache.org>
Tested-by: Alexey Serbin <alexey@apache.org>