unit-def: introduce freezer_state_objective()

No functional change, preparation for later commits.

src/basic/unit-def.c

@@ -144,6 +144,16 @@ FreezerState freezer_state_finish(FreezerState state) {
         return freezer_state_finish_table[state];
 }
 
+FreezerState freezer_state_objective(FreezerState state) {
+        FreezerState objective;
+
+        objective = freezer_state_finish(state);
+        if (objective == FREEZER_FROZEN_BY_PARENT)
+                objective = FREEZER_FROZEN;
+
+        return objective;
+}
+
 static const char* const unit_marker_table[_UNIT_MARKER_MAX] = {
         [UNIT_MARKER_NEEDS_RELOAD]  = "needs-reload",
         [UNIT_MARKER_NEEDS_RESTART] = "needs-restart",