IP Address use case validation

-validates IPAddress/gateway using inet_pton api.
-validates prefix length for ipv4/ipv6.
-if dhcp is enabled, it won't allow to set ip/gateway.

Resolves openbmc/openbmc#1671

Change-Id: I76c1d9d11dfb59002eb1310d87e94ee622714a4a
Signed-off-by: Nagaraju Goruganti <ngorugan@in.ibm.com>
5 files changed