Fix unexpected change of ipsrc of ipv6
Fix unexpected change of ipsrc of ipv6

Issue: The initial ipsrc of ipv6 is dhcp. When setting different static
ipv4 twice, ipv6 will become static.

Fix: Rewrite the if condition. setDHCPv4Property is only for IPv4
management. It should not modify IPv6 state.

Tested: Verified step as below:

1. Get dbus property 'DHCPEnabled' via
busctl get-property xyz.openbmc_project.Network
/xyz/openbmc_project/network/eth1
xyz.openbmc_project.Network.EthernetInterface DHCPEnabled
s "xyz.openbmc_project.Network.EthernetInterface.DHCPConf.both"

2. Set an static ipv4.
3. Set another static ipv4.
4. Check 'DHCPEnabled' is still v6 via dbus. And check the config
in 00-bmc-eth1.network without ipv6 static address.

Change-Id: I8b55c01a61e568555983fc462d4508f2860217be
Signed-off-by: Tony Lee <39789b450c786ba33eb2c19b3da697ab6ba83d1e@quantatw.com>

openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid