RFR(T) 8233855 [TESTBUG] appcds/FieldLayoutFlags.java failed to clean up files after test

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8233855

In the test library code used by this test, the following close() is 
missing.
For some reason, the problem shows up only in this test, probably 
because this
test has opened the zipfile more often than other test cases.

$ hg diff
diff -r ad157fab6bf5 test/hotspot/jtreg/runtime/cds/appcds/TestCommon.java
--- a/test/hotspot/jtreg/runtime/cds/appcds/TestCommon.java    Thu Nov 
07 16:26:57 2019 -0800
+++ b/test/hotspot/jtreg/runtime/cds/appcds/TestCommon.java    Fri Nov 
08 10:50:08 2019 -0800
@@ -343,6 +343,7 @@
              newFile.renameTo(oldFile);
              System.out.println("firstJar = " + firstJar + " Modified");
          } else {
+            zipFile.close();
              System.out.println("firstJar = " + firstJar);
          }
      }

I ran the test again in tier4 and now it passed.

Thanks
- Ioi