Use pre-increment in action point tests

src/test/cpp/net/eagle0/shardok/library/action_point_distances/ActionPointDistances_test.cpp

@@ -28,11 +28,11 @@ class ActionPointDistancesTest : public ::testing::Test {
         //  P P P M P P
 
         // const_cast is safe because we own the mutable buffer (map)
-        for (int i = 6; i < 12; i++) {
+        for (int i = 6; i < 12; ++i) {
             const_cast<Terrain*>(map->mutable_terrain()->GetMutableObject(i))
                     ->mutate_type(net::eagle0::shardok::storage::fb::Terrain_::Type_FOREST);
         }
-        for (int i = 18; i < 24; i++) {
+        for (int i = 18; i < 24; ++i) {
             const_cast<Terrain*>(map->mutable_terrain()->GetMutableObject(i))
                     ->mutate_type(net::eagle0::shardok::storage::fb::Terrain_::Type_RIVER);
         }