pipe-loader: teardown the winsys, if create_screen fails
pipe-loader: teardown the winsys, if create_screen fails

i.e. plug some (hard to hit) memory leaks.

v2: fix rebase fallout - really teardown the winsys (Brian)
Signed-off-by: Emil Velikov <4c996f2f093ddd0585a556460b4cc3ba555546ef@gmail.com>
Acked-by: Rob Clark <6f78cdb10adbe0a7fbbf4098125a51f401c77a5f@freedesktop.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler