va: fix the fd leak issue caused by vaInitialize failure

[XinfengZhang]

Fixes #741

[evelikov]

Instead, the display specifics should be moved from vaInitialize to vaGetDisplay* time, although that's not particularly clear and easy with the current vaGetDisplay API. Ideally VAAPI will evolve an https://registry.khronos.org/EGL/sdk/docs/man/html/eglGetPlatformDisplay.xhtml like API - adding the other "Platform" APIs from EGL_EXT_platform_base (or similar extensions) would be a wise move IMHO.