severe memory leak caused by broken palette_destroy() function

The following commit breaks the code of the function palette_destroy().

http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=commit;h=e31e3694afef58ba191cbcc6875ec243e5971268

The broken code causes a severe memory leak of 'VncPalette' structures
because it never frees anything:

     70 void palette_destroy(VncPalette *palette)
     71 {
     72     if (palette == NULL) {
     73         qemu_free(palette);
     74     }
     75 }

Version 2 of the patch calls qemu_free() unconditionally.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
