core: Static IP is set as none bootproto for cloud-init

1. Setting the bootproto for static if not dhcp (was set as none)
2. Adding display name for NetworkBootProtocol enum
3. Fix CloudInitHandler for sending nulls for ip and subnet on dhcp bootproto.

Change-Id: I53159a6ead92d890f7abe2ec78196bb967994a5f
Bug-Url: https://bugzilla.redhat.com/1036013
Signed-off-by: Shahar Havivi <shaharh@redhat.com>