Get HardLink test in //runsc/fsgofer:lisafs_test to pass.

This test was attempting to create a link with the same name as the target.
Changed that to use a different name for link. This test also exposed a ref
count bug in LISAFS RPC handlers. Fixed that.

Updates #8688

PiperOrigin-RevId: 516912550

pkg/lisafs/handlers.go

@@ -892,6 +892,7 @@ func LinkAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32,
 	if err != nil {
 		return 0, err
 	}
+	defer targetFD.DecRef(nil)
 	if targetFD.IsDir() {
 		// Can not create hard link to directory.
 		return 0, unix.EPERM

pkg/lisafs/testsuite/testsuite.go

@@ -490,7 +490,8 @@ func testHardLink(ctx context.Context, t *testing.T, tester Tester, root lisafs.
 	defer closeFD(ctx, t, fd)
 	defer unix.Close(hostFD)
 
-	link, linkStat := link(ctx, t, root, name, controlFile)
+	linkName := "linkFile"
+	link, linkStat := link(ctx, t, root, linkName, controlFile)
 	defer closeFD(ctx, t, link)
 
 	if linkStat.Ino != fileIno.Ino {