arb_texture_view/rendering-formats: texelFetching invalid float

With commit 1b071c63, this piglit test starts clearing float textures to 0xffffffff with an integer-formatted view. It then attempts to texelFetch this value with the original float format.

This value is an invalid/undefined float, so it's undefined what the HW will return during the texelFetch operation. On intel, the HW seems to match the test's expectation for all float formats except for RGBX32_FLOAT.

/cc @mareko

Edit: Since a conversation has already started based on the above, please see a clarification of the issue here: #42 (comment 689509)