KUDU-1923: rpc_encryption flag is not enforced

The rpc_encryption flag wasn't being taken into account during
negotiation, so TLS encryption was in effect optional regardless of
configuration.

Change-Id: Ifdf17c6bb59ca4af1215376c5221a90bd1d93b64
Reviewed-on: http://gerrit.cloudera.org:8080/6342
Reviewed-by: Todd Lipcon <todd@apache.org>
Tested-by: Kudu Jenkins
11 files changed