8325189: Enable this-escape javac warning in java.base

Reviewed-by: alanb, erikj, naoto, smarks, ihse, joehw, lancea, weijun

src/java.base/unix/classes/sun/nio/fs/UnixFileSystemProvider.java

@@ -74,6 +74,7 @@ public abstract class UnixFileSystemProvider
     private static final byte[] EMPTY_PATH = new byte[0];
     private final UnixFileSystem theFileSystem;
 
+    @SuppressWarnings("this-escape")
     public UnixFileSystemProvider() {
         theFileSystem = newFileSystem(StaticProperty.userDir());
     }