Observed once in jdk10 CI run.

Please refer to the test outpt below:
command: main BasicLongCredentials
reason: Assumed action based on file name: run main BasicLongCredentials
Mode: agentvm
Agent id: 7
elapsed time (seconds): 0.01
...
----------System.err:(19/1421)----------
java.io.IOException: Server returned HTTP response code: 401 for URL: http://localhost:63414/test/
at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1895)
at java.base/sun.net.www.protocol.http.HttpURLConnection.access$200(HttpURLConnection.java:97)
at java.base/sun.net.www.protocol.http.HttpURLConnection$9.run(HttpURLConnection.java:1483)
at java.base/sun.net.www.protocol.http.HttpURLConnection$9.run(HttpURLConnection.java:1481)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.AccessController.doPrivilegedWithCombiner(AccessController.java:793)
at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1480)
at BasicLongCredentials.main(BasicLongCredentials.java:71)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)