ClosedFileSystemException when I run demo

[decebals]

Today, after I released version 3.3.0 I wanted to replicate some old issues.
When I tried to replicate #253 (run demo in command line via run-demo.sh script - I use a Linux for development), I retrieved the following error:

2020-04-21 20:34:48,706 DEBUG org.pf4j.AbstractExtensionFinder - Finding extensions of extension point 'org.pf4j.demo.api.Greeting'
2020-04-21 20:34:48,706 DEBUG org.pf4j.ServiceProviderExtensionFinder - Reading extensions storages from classpath
2020-04-21 20:34:48,707 DEBUG org.pf4j.ServiceProviderExtensionFinder - Read 'file:/home/decebal/work/pf4j/demo-dist/pf4j-demo.jar!/META-INF/services'
Exception in thread "main" java.nio.file.ClosedFileSystemException
	at jdk.zipfs/jdk.nio.zipfs.ZipFileSystem.ensureOpen(ZipFileSystem.java:1105)
	at jdk.zipfs/jdk.nio.zipfs.ZipFileSystem.getFileAttributes(ZipFileSystem.java:313)
	at jdk.zipfs/jdk.nio.zipfs.ZipPath.getAttributes(ZipPath.java:727)
	at jdk.zipfs/jdk.nio.zipfs.ZipFileSystemProvider.readAttributes(ZipFileSystemProvider.java:293)
	at java.base/java.nio.file.Files.readAttributes(Files.java:1763)
	at java.base/java.nio.file.FileTreeWalker.getAttributes(FileTreeWalker.java:219)
	at java.base/java.nio.file.FileTreeWalker.visit(FileTreeWalker.java:276)
	at java.base/java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:322)
	at java.base/java.nio.file.Files.walkFileTree(Files.java:2716)
	at org.pf4j.ServiceProviderExtensionFinder.readExtensions(ServiceProviderExtensionFinder.java:135)
	at org.pf4j.ServiceProviderExtensionFinder.collectExtensions(ServiceProviderExtensionFinder.java:130)
	at org.pf4j.ServiceProviderExtensionFinder.collectExtensions(ServiceProviderExtensionFinder.java:118)
	at org.pf4j.ServiceProviderExtensionFinder.readClasspathStorages(ServiceProviderExtensionFinder.java:69)
	at org.pf4j.AbstractExtensionFinder.readStorages(AbstractExtensionFinder.java:301)
	at org.pf4j.AbstractExtensionFinder.getEntries(AbstractExtensionFinder.java:309)
	at org.pf4j.AbstractExtensionFinder.find(AbstractExtensionFinder.java:56)
	at org.pf4j.DefaultExtensionFinder.find(DefaultExtensionFinder.java:45)
	at org.pf4j.AbstractPluginManager.getExtensions(AbstractPluginManager.java:550)
	at org.pf4j.demo.Boot.main(Boot.java:62)
/home/decebal/work/pf4j

After some investigation, I realized that the error was introduced by commit 0794f5c in an attempt to solve #355.
I think that we should close the FileSystem only for Windows OS. On Linux and probably on other Unix flavor OS, the close of FileSystem throws ClosedFileSystemException.