glsl: Initialize lower_shared_reference_visitor members.
Fix defects reported by Coverity Scan.
Uninitialized scalar field (UNINIT_CTOR) uninit_member: Non-static class member buffer_access_type is not initialized in this constructor nor in any functions that it calls. uninit_member: Non-static class member progress is not initialized in this constructor nor in any functions that it calls.
Signed-off-by: Vinson Lee vlee@freedesktop.org