ipn: apply tailnet-wide default for auto-updates (#10508)

When auto-update setting in local Prefs is unset, apply the tailnet
default value from control. This only happens once, when we apply the
default (or when the user manually overrides it), tailnet default no
longer affects the node.

Updates #16244

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

cmd/tailscale/cli/cli_test.go

@@ -558,7 +558,6 @@ func TestPrefsFromUpArgs(t *testing.T) {
 				AllowSingleHosts: true,
 				AutoUpdate: ipn.AutoUpdatePrefs{
 					Check: true,
-					Apply: false,
 				},
 			},
 		},
@@ -575,7 +574,6 @@ func TestPrefsFromUpArgs(t *testing.T) {
 				NetfilterMode:    preftype.NetfilterOn,
 				AutoUpdate: ipn.AutoUpdatePrefs{
 					Check: true,
-					Apply: false,
 				},
 			},
 		},
@@ -594,7 +592,6 @@ func TestPrefsFromUpArgs(t *testing.T) {
 				NetfilterMode: preftype.NetfilterOn,
 				AutoUpdate: ipn.AutoUpdatePrefs{
 					Check: true,
-					Apply: false,
 				},
 			},
 		},
@@ -684,7 +681,6 @@ func TestPrefsFromUpArgs(t *testing.T) {
 				NoSNAT:        true,
 				AutoUpdate: ipn.AutoUpdatePrefs{
 					Check: true,
-					Apply: false,
 				},
 			},
 		},
@@ -701,7 +697,6 @@ func TestPrefsFromUpArgs(t *testing.T) {
 				NoSNAT:        true,
 				AutoUpdate: ipn.AutoUpdatePrefs{
 					Check: true,
-					Apply: false,
 				},
 			},
 		},
@@ -720,7 +715,6 @@ func TestPrefsFromUpArgs(t *testing.T) {
 				},
 				AutoUpdate: ipn.AutoUpdatePrefs{
 					Check: true,
-					Apply: false,
 				},
 			},
 		},