net/dns: disable NetworkManager and resolved configurators temporarily.

They need some rework to do the right thing, in the meantime the direct
and resolvconf managers will work out.

The resolved implementation was never selected due to control-side settings.
The networkmanager implementation mostly doesn't get selected due to
unforeseen interactions with `resolvconf` on many platforms.
Both implementations also need rework to support the various routing modes
they're capable of.

Signed-off-by: David Anderson <danderson@tailscale.com>

net/dns/manager_linux.go

@@ -8,10 +8,11 @@ import "tailscale.com/types/logger"
 
 func newManager(logf logger.Logf, interfaceName string) OSConfigurator {
 	switch {
-	case isResolvedActive():
+	// TODO: rework NetworkManager and resolved support.
-		return newResolvedManager()
+	// case isResolvedActive():
-	case isNMActive():
+	// 	return newResolvedManager()
-		return newNMManager(interfaceName)
+	// case isNMActive():
+	// 	return newNMManager(interfaceName)
 	case isResolvconfActive():
 		return newResolvconfManager(logf)
 	default:

net/dns/nm.go

@@ -4,6 +4,8 @@
 
 // +build linux
 
+//lint:file-ignore U1000 refactoring, temporarily unused code.
+
 package dns
 
 import (

net/dns/resolved.go

@@ -4,6 +4,8 @@
 
 // +build linux
 
+//lint:file-ignore U1000 refactoring, temporarily unused code.
+
 package dns
 
 import (