Some unit tests aren't reliably closing open files; invariably these were written prior to (or without utilizing) try-with-resources.

Leaving files and other resources open can cause problems during automated builds, etc. See JDK-7127924 for example.

These tests should be updated to use try-with-resource.

Examples:
* 6400872/T6400872.java (line 127)
* 6638501/JarFromManifestFailure.java (line 147)
* T8152616.java (line 63, 69)