Transfer-encoding: chucked in HTTP Header Manager caused error

**faither7** ([Bug 63917](https://bz.apache.org/bugzilla//show_bug.cgi?id=63917&redirect=false)):
When Transfer-Encoding header is added in HTTP Header Manager, running a Jemter test plan caused the following error.
org.apache.http.client.ClientProtocolException
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:187)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at org.apache.jmeter.protocol.http.sampler.HTTPHC4Impl.executeRequest(HTTPHC4Impl.java:850)
at org.apache.jmeter.protocol.http.sampler.HTTPHC4Impl.sample(HTTPHC4Impl.java:561)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerProxy.sample(HTTPSamplerProxy.java:67)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java:1282)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java:1271)
at org.apache.jmeter.threads.JMeterThread.doSampling(JMeterThread.java:627)
at org.apache.jmeter.threads.JMeterThread.executeSamplePackage(JMeterThread.java:551)
at org.apache.jmeter.threads.JMeterThread.processSampler(JMeterThread.java:490)
at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:257)
at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.http.ProtocolException: Transfer-encoding header already present
at org.apache.http.protocol.RequestContent.process(RequestContent.java:94)
at org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:133)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:184)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
... 11 more

Created attachment [HTTPManager_ScreenShot.jpg](https://apache.github.io/jmeter-bugzilla-attachments/17/63917/36881/HTTPManager_ScreenShot.jpg): Screen shot of HTTP Header Manager

Severity: major
OS: