Fix the triggering of guard conditions. (#504)

When a guard condition goes active, we have to remember
to increase the trig_idx so we look at the next trigger.
Otherwise, we can get into situations where we skip a
triggered member.

Signed-off-by: Chris Lalancette <[email protected]>

rmw_cyclonedds_cpp/src/rmw_node.cpp

@@ -4492,6 +4492,7 @@ extern "C" rmw_ret_t rmw_wait(
         if (ws->trigs[trig_idx] == static_cast<dds_attach_t>(nelems)) {
           bool dummy;
           dds_take_guardcondition(x->gcondh, &dummy);
+          trig_idx++;
         } else {
           gcs->guard_conditions[i] = nullptr;
         }