default is libcontainer which doesn't use any other driver:
https://blog.docker.com/2014/03/docker-0-9-introducing-execution-drivers-and-libcontainer/
Summary: Docker: the open-source application container engine
Name: docker
Version: 1.3.3
-Release: 0.4
+Release: 0.5
License: Apache v2.0
Group: Applications/System
Source0: https://github.com/docker/docker/archive/v%{version}/%{name}-%{version}.tar.gz
Requires(pre): /usr/sbin/groupadd
Requires: iproute2 >= 3.5
Requires: iptables
-Requires: lxc >= 0.8
Requires: rc-scripts >= 0.4.0.10
Requires: tar >= 1:1.26
Requires: uname(release) >= 3.8