NIFI-4700: Moved all PostHTTP http clients, http responses to try-with-resources

[m-hogue]

… to make sure they're closed

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[mosermw]

Hi @m-hogue I got an error when trying to test PostHTTP sending to a ListenHTTP with this PR.

2018-02-02 22:15:43,007 ERROR [Timer-Driven Process Thread-7] o.a.nifi.processors.standard.PostHTTP PostHTTP[id=01611004-47b6-1aa6-0836-08b0dc270fae] Failed to Post StandardFlowFileRecord[uuid=ac9ba210-264f-43
b3-bfcf-34bc4c566932,claim=StandardContentClaim [resourceClaim=StandardResourceClaim[id=1517609573204-1, container=default, section=1], offset=364938, length=121646],offset=0,name=nifi-app.log.txt,size=121646]
to http://localhost:7777/contentListener: sent content and received status code 303:See Other but no Hold URI
2018-02-02 22:15:43,020 ERROR [Timer-Driven Process Thread-7] o.a.nifi.processors.standard.PostHTTP PostHTTP[id=01611004-47b6-1aa6-0836-08b0dc270fae] PostHTTP[id=01611004-47b6-1aa6-0836-08b0dc270fae] failed to
process due to java.lang.IllegalStateException: Connection pool shut down; rolling back session: {}
java.lang.IllegalStateException: Connection pool shut down
at org.apache.http.util.Asserts.check(Asserts.java:34)
at org.apache.http.pool.AbstractConnPool.lease(AbstractConnPool.java:184)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.requestConnection(PoolingHttpClientConnectionManager.java:257)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:176)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:111)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108)
at org.apache.nifi.processors.standard.PostHTTP.onTrigger(PostHTTP.java:643)
at org.apache.nifi.processor.AbstractProcessor.onTrigger(AbstractProcessor.java:27)
at org.apache.nifi.controller.StandardProcessorNode.onTrigger(StandardProcessorNode.java:1122)
at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:147)
at org.apache.nifi.controller.tasks.ContinuallyRunProcessorTask.call(ContinuallyRunProcessorTask.java:47)
at org.apache.nifi.controller.scheduling.TimerDrivenSchedulingAgent$1.run(TimerDrivenSchedulingAgent.java:128)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)