40network: Copy the customize dhcp config

40network: Copy the customize dhcp config

It is not available to valid the customize dhcp config
/etc/dhclient.conf in the initram environment.

Dracut uses the default follow config to construct the initramfs.

request subnet-mask, broadcast-address, time-offset, routers,
        domain-name, domain-name-servers, domain-search, host-name,
        root-path, interface-mtu;

Copy the customize config to make the config availably in the
initram environment.

Signed-off-by: Minfei Huang <mhuang@redhat.com>