Fix for PR22931, assertion failure with attributes and templates.
When cloning a scope, the constructor of LocalInstantiationScope will set the current scope in Sema to be that new scope. However, cloning scopes doesn't change what the current scope should be. This manifests when multiple late parsed attributed are used. The first attribute has a properly cloned scope, but the other attributes get the wrong scope. The assertion in PR22931 is triggered when a Decl is looked up within an incorrect scope and is not found.