8358077: sun.tools.attach.VirtualMachineImpl::checkCatchesAndSendQuitTo on Linux leaks file handles after JDK-8327114

Reviewed-by: kevinw, sspitsyn, syan

Author: larry-cable

src/jdk.attach/linux/classes/sun/tools/attach/VirtualMachineImpl.java

@@ -35,6 +35,8 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 
+import java.util.Optional;
+
 import java.util.regex.Pattern;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
@@ -358,7 +360,11 @@ private static boolean checkCatchesAndSendQuitTo(int pid, boolean throwIfNotRead
         if (okToSendQuit) {
             sendQuitTo(pid);
         } else if (throwIfNotReady) {
-            final var cmdline = Files.lines(procPid.resolve("cmdline")).findFirst();
+            Optional<String> cmdline = Optional.empty();
+
+            try (final var clf = Files.lines(procPid.resolve("cmdline"))) {
+                cmdline = clf.findFirst();
+            }
 
             var cmd = "null"; // default