mesa: Make a function is_transform_feedback_active_and_unpaused.

mesa: Make a function is_transform_feedback_active_and_unpaused.

The rather unweildy logic for determining this condition was repeated
in a large number of places.  This patch consolidates it to a single
inline function.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>