Middle manager rolling upgrade issue with TLS support

[jon-wei]

Issue first reported here by @erikdubbelboer:
#4536 (comment)

If I have a 0.10.0 cluster running, and I upgrade only the middleManager to a version of Druid that includes #4270, batch ingestion tasks fail with the following exception:

2017-07-21T01:29:16,989 WARN [main] io.druid.indexing.common.actions.RemoteTaskActionClient - Exception submitting action for task[index_wikiticker_2017-07-21T01:28:40.434Z]
java.io.IOException: Failed to locate service uri
	at io.druid.indexing.common.actions.RemoteTaskActionClient.submit(RemoteTaskActionClient.java:94) [druid-indexing-service-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.indexing.common.task.IndexTask.isReady(IndexTask.java:159) [druid-indexing-service-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.indexing.worker.executor.ExecutorLifecycle.start(ExecutorLifecycle.java:169) [druid-indexing-service-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_51]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_51]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_51]
	at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_51]
	at io.druid.java.util.common.lifecycle.Lifecycle$AnnotationBasedHandler.start(Lifecycle.java:364) [java-util-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.java.util.common.lifecycle.Lifecycle.start(Lifecycle.java:263) [java-util-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.guice.LifecycleModule$2.start(LifecycleModule.java:156) [druid-api-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.cli.GuiceRunnable.initLifecycle(GuiceRunnable.java:101) [druid-services-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.cli.CliPeon.run(CliPeon.java:283) [druid-services-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.cli.Main.main(Main.java:108) [druid-services-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
Caused by: java.lang.NullPointerException
	at io.druid.curator.discovery.ServerDiscoverySelector$1.apply(ServerDiscoverySelector.java:60) ~[druid-server-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.curator.discovery.ServerDiscoverySelector$1.apply(ServerDiscoverySelector.java:52) ~[druid-server-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.curator.discovery.ServerDiscoverySelector.pick(ServerDiscoverySelector.java:108) ~[druid-server-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.indexing.common.actions.RemoteTaskActionClient.getServiceInstance(RemoteTaskActionClient.java:164) ~[druid-indexing-service-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	at io.druid.indexing.common.actions.RemoteTaskActionClient.submit(RemoteTaskActionClient.java:89) ~[druid-indexing-service-0.11.0-SNAPSHOT.jar:0.11.0-SNAPSHOT]
	... 12 more

This is caused by instance.getSslPort() returning null:

      final int port = instance.getSslPort() >= 0 ? instance.getSslPort() : instance.getPort();