Fix #37109: missing cycles texture display in edit mode.

My previous fix for uninitialized texture coordinates was not working well,
and in fact there was a bigger issue with GLSL drawing and missing attributes
with immediate draw mode. Now it will explicitly pass zero rather than having
it use whatever value was set last.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60821 954f8c5b-7b00-dc11-b283-0030488c597c