This patch labels geometry_shading.vertex_transform_feedback.* as
"SKIP" instead of "FAIL" to fix some failures in dEQP tests.

OpenGL ES 3.1 extension GL_EXT_geometry_shader requires additional
validations on transform feedback, which hasn't been implemented
in ANGLE, so geometry_shading.vertex_transform_feedback.* fail just
after beginTransformfeedback(). As endTransformfeedback() isn't
called in dEQP function resetStateES():
1. An error occurs in this function when trying to clear transform
   feedback.
2. Some of the tests afterwards also fail because it isn't allowed
   to change active program by useProgram() when transform feedback
   is on.

So it is better to skip these tests before ANGLE supports these new
features.

BUG=angleproject:1941

Change-Id: I8834f71e6a655f18118ee4ecf26f4118da6de2f1
Reviewed-on: https://chromium-review.googlesource.com/843955
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jiajia Qin <jiajia.qin@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>