runtime/internal/flow/manager: Dials should cancel when the context cancels.
runtime/internal/flow/manager: Dials should cancel when the context
cancels.

Right now the dials are left hanging, which prevents the client from
exiting and therefore the runtime from shutting down.

Change-Id: I6606cc58e1a3b0019915a7a21bba90137e4d00a0

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