Launcher test PatchSystemModules.java fails frequently after JDK-8234049

test/jdk/tools/launcher/modules/patch/systemmodules/PatchSystemModules.java

This test start failing frequently after JDK-8234049, failure reproducible with windows-x64 in 20 times of run.

In case of fail, it failed in PatchSystemModules.test():

Command line: [C:\\users\\opc\\sandbox_keepme\\jdk\\bin\\java.exe --module-path mods -m m1/p1.Main 1]
...
Command line: [C:\\users\\opc\\sandbox_keepme\\jdk\\bin\\java.exe --patch-module java.base=patches\\java.base --module-path mods -m m1/p1.Main 1]
[2020-01-03T10:05:00.529828300Z] Gathering output for process 20324
Error occurred during initialization of boot layer
java.lang.InternalError: java.lang.NullPointerException
Caused by: java.lang.NullPointerException

Error occurred during initialization of boot layer
java.lang.InternalError: java.lang.NullPointerException
Caused by: java.lang.NullPointerException
...
test PatchSystemModules.test(): failure
java.lang.AssertionError: expected [true] but found [false]
at org.testng.Assert.fail(Assert.java:94)
at org.testng.Assert.failNotEquals(Assert.java:496)
at org.testng.Assert.assertTrue(Assert.java:42)
at org.testng.Assert.assertTrue(Assert.java:52)
at PatchSystemModules.runTest(PatchSystemModules.java:216)
at PatchSystemModules.test(PatchSystemModules.java:119)
...
===============================================
tools/launcher/modules/patch/systemmodules/PatchSystemModules.java
Total tests run: 4, Failures: 1, Skips: 0
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