control/controlclient: clean up various things in prep for state overhaul

We want the overall state (used only for tests) to be computed from
the individual states of each component, rather than moving the state
around by hand in dozens of places.

In working towards that, we found a lot of things to clean up.

Updates #cleanup

Change-Id: Ieaaae5355dfae789a8ec7a56ce212f1d7e3a92db
Co-authored-by: Maisem Ali <maisem@tailscale.com>
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/controlclient_test.go

@@ -50,12 +50,7 @@ func TestStatusEqual(t *testing.T) {
 			true,
 		},
 		{
-			&Status{state: StateNew},
-			&Status{state: StateNew},
-			true,
-		},
-		{
-			&Status{state: StateNew},
+			&Status{},
 			&Status{state: StateAuthenticated},
 			false,
 		},