Use g_path_get_basename to get the directory components of
a file name, and free its return when no longer needed.

Signed-off-by: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
Message-Id: <1459997185-15669-3-git-send-email-weijg.fnst@cn.fujitsu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>