Add DBConnector::getall() method and refactor ConfigDBConnector_Native::get_config().#692

liuh-80 merged 1 commit intosonic-net:mastersonic-net/sonic-swss-common:masterfrom

liuh-80:dev/liuh/refact-getallliuh-80/sonic-swss-common:dev/liuh/refact-getallCopy head branch name to clipboard