store: invoke "os.path.isdir()" via vfs This patch invokes "os.path.isdir()" via "rawvfs" object to avoid filename encoding, because the path passed to "os.path.isdir()" shouldn't be encoded. This patch newly adds "self.rawvfs" field only to "basicstore" and "encodedstore", because "fncachestore" has "self.rawvfs" already.