ref: Remove flow.Manager connection method.
ref: Remove flow.Manager connection method.

Dialing flows is virtually free, so no need to expose connection
method from flow.Manager.

Change-Id: I6b4d9759d426abfffaa6c9f6c4bafec1bb8c362c
MultiPart: 2/2

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref