connmgr: Use same Dial func signature as net.Dial

[jrick]

No description provided.

[davecgh]

We'll need to talk to the folks who made the upstream change before I approve this. I believe it was changed specifically to allow a use case needed by the LN devs, so I don't want to undo it without having a conversation first.

[davecgh]

After digging into this some more, the intention of the upstream change was to allow the internal structures to use a net.Addr for GetNewAddress and Connect. The Dial function itself doesn't need to take the net.Addr directly since the caller can always just do .Diala(ddr.Network(), addr.String()) to achieve the same effect.