Add support for IPsec phase 1 ID of IPv4 address format

Some IPsec VPN router commonly used in Japan don't use Global IPv4 address as IPsec phase 1 ID.
Moreover they cannot set IPsec phase 1 ID as FQDN format (like "@foo") when Main mode.

This patch add support for IPsec phase 1 ID of IPv4 address format like below.

# set vpn ipsec site-to-site peer @foo authentication remote-id 192.168.1.1

I want you to merge because there are a lot of Japanese people who be saved this problem is fixed.