Fixed caching for table schema with prefix

I use `tablePrefix` in the framework. There are 2 tables with same name but different prefix. For example: `enState` and `ruState`, where **en** and **ru** prefix. 
In the AR (StateModel) method *tableName* return `{{State}}`.
When I enable cache and use AR for State with prefix `en` for example, the table schema will be cached for `enState`. Further, If I change prefix to `ru` the method CDbSchema::getTable() returns still `enState`. 

If `key` for cache will be based on the `realName`, It will resolve the issue.