[Libva] Directly encoding a surface after decoding

[Timo Rothenpieler]

Indeed, the library which contains the initialisation code was reloaded 
between the calls which caused the initialization-routine to be run 
twice, but not my checks if it's the same Display.
Sorry for the mess, it seems to work fine now.
Now just a bit of polishing and a lot of testing, and maybe there'll be 
a vaapi transcoding version of vlc soon.

> Hi,
>     From the tracelog it seems that both the decoding and encoding call
> the function of vaInitialize, which will initialize the different
> display context for decoding and encoding. In such case the surface ID
> can't be shared correctly between decoding/encoding.
>     Will you please also call the vaInitialize only once for
> decoding/encoding and then see whether it is helpful?
>
> Best regards.
>      Yakui