Large amounts of DNS requests with MagicDNS enabled on Linux hosts

### What is the issue?

I run my own DNS resolver (dnsmasq) on my local network, as well as having MagicDNS enabled, with no global nameservers set on the Tailscale side. Every DNS query that the Linux hosts make ends up creating between 100 and 15,000+(!) DNS queries to my resolver. This only happens when the requests are resolved via `100.100.100.100`, not when I query the gateway or my resolver itself. This also only happens on Linux machines — not macOS.

### Steps to reproduce

1. Enable MagicDNS with no global nameservers
2. Make DNS requests to non-Tailscale hosts on Linux

### Are there any recent changes that introduced the issue?

_No response_

### OS

Linux

### OS version

NixOS 23.11

### Tailscale version

1.56.1

### Other software

_No response_

### Bug report

BUG-946d6bad4ad2cd5bb9301f80e088e30cea12ea07857c64206afbdd367d257993-20240417034040Z-4224a33e3939fd02