For LB device in inline mode, the ip deployer(the owner of public ip) is the
firewall in front of it, not itself. So check if it's inline or not, if it's
inline, return the firewall as ip deployer
Introduce the concept of Ip Deployer. The IP deployer would be responible for
apply IP to the element. Most element's IP deployer is itself, but it can be
someone else if we want to implement inline mode in the future.
Added PortForwardingServiceProvider, StaticNatServiceProvider, rename
PasswordServiceProvider to UserDataServiceProvider(may rename to a better name
later).
Add related function for service providers.