HTTP segment load/drop peons getting unauthorized

[gianm]

Noticed this when testing #4874 on a cluster with authentication enabled. Perhaps it needs to use an escalated http client?

2018-02-02T08:15:28,336 ERROR [Master-PeonExec--0] io.druid.server.coordinator.HttpLoadQueuePeon - Request[https://ip-172-31-3-17.ec2.internal:8283/druid-internal/v1/segments/changeRequests?timeout=300000] Failed with status[401]. Reason[Unauthorized].
io.druid.java.util.common.RE: Unexpected Response Status.
        at io.druid.server.coordinator.HttpLoadQueuePeon$3.onSuccess(HttpLoadQueuePeon.java:248) [druid-server-0.12.0-SNAPSHOT.jar:0.12.0-SNAPSHOT]
        at io.druid.server.coordinator.HttpLoadQueuePeon$3.onSuccess(HttpLoadQueuePeon.java:205) [druid-server-0.12.0-SNAPSHOT.jar:0.12.0-SNAPSHOT]
        at com.google.common.util.concurrent.Futures$4.run(Futures.java:1181) [guava-16.0.1.jar:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_152]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_152]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [?:1.8.0_152]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [?:1.8.0_152]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_152]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_152]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_152]

/cc @himanshug