racktables_ipv4_allocation should return data consistent with the lookups

[cwilloughby-bw]

Currently, after creating a new IPV4 allocation, it simply returns the IPv4 address that was allocated. Although this is technically correct, it would be nicer + easier to work with if it returned data consistent with the other lookups:

ok: [storage-01-rdu.lab1.bandwidthclec.local] => (item=vs_NFS-test_vol_01) => {
"msg": {
"address": "192.168.112.202",
"gateway": "192.168.112.193",
"ifname": "vs_NFS-test_vol_01",
"netmask": "255.255.255.192",
"netname": "LAB1-DC-Storage2",
"vlan": 135
}
}