Function of enter_to_ns() is useful but currently is static for
lxccontainer.c.

This patch split it into two parts named as switch_to_newuser()
and switch_to_newnet() into utils.c.
Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>