ssh/tailssh, ipnlocal, controlclient: fetch next SSHAction from network

Updates #3802

Change-Id: I08e98805ab86d6bbabb6c365ed4526f54742fd8e
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipnlocal/state_test.go

@@ -6,6 +6,7 @@ package ipnlocal
 
 import (
 	"context"
+	"net/http"
 	"sync"
 	"testing"
 	"time"
@@ -266,6 +267,10 @@ func (*mockControl) SetDNS(context.Context, *tailcfg.SetDNSRequest) error {
 	panic("unexpected SetDNS call")
 }
 
+func (*mockControl) DoNoiseRequest(*http.Request) (*http.Response, error) {
+	panic("unexpected DoNoiseRequest call")
+}
+
 // A very precise test of the sequence of function calls generated by
 // ipnlocal.Local into its controlclient instance, and the events it
 // produces upstream into the UI.