[CF-458] Set enable_dhcp to original value on destination.
[CF-458] Set enable_dhcp to original value on destination.

The bug was introduced which caused all subnets change its enable_dhcp to
False during VM migration. This patch fixes this.

MirantisWorkloadMobility/CloudFerry,SVilgelm/CloudFerry,SVilgelm/CloudFerry,MirantisWorkloadMobility/CloudFerry,MirantisWorkloadMobility/CloudFerry,MirantisWorkloadMobility/CloudFerry,SVilgelm/CloudFerry,SVilgelm/CloudFerry