vbo: ignore primitive restart if FixedIndex is enabled in DrawArrays

vbo: ignore primitive restart if FixedIndex is enabled in DrawArrays

From GL 4.4 Core profile:

  If both PRIMITIVE_RESTART and PRIMITIVE_RESTART_FIXED_INDEX are
  enabled, the index value determined by PRIMITIVE_RESTART_FIXED_INDEX is
  used. If PRIMITIVE_RESTART_FIXED_INDEX is enabled, primitive restart is not
  performed for array elements transferred by any drawing command not taking a
  type parameter, including all of the *Draw* commands other than *DrawEle-
  ments*.

Cc: 10.2 10.3 10.4 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>