[daemon] fails to locate images early on start

Given these steps:
```bash
curl --location --output multipass.pkg https://multipass.run/download/macos
sudo installer -dumplog -target / -pkg multipass.pkg

multipass find
multipass start || sleep 10
multipass start
multipass list
```

If a system/network is slow enough, it will fail to find images immediately on startup:

```plain
...
installer: Package name is multipass
installer: Installing at base path /
installer: The install was successful.
No images found.
launch failed: Remote "" is unknown or unreachable.
[2021-03-05T09:23:36.942] [info] [rpc] gRPC listening on unix:/var/run/multipass_socket, SSL:on
[2021-03-05T09:23:36.964] [warning] [Qt] QIODevice::write (QFile, "/var/root/Library/Caches/multipassd/vault/multipassd-image-records.json"): device not open
[2021-03-05T09:23:36.969] [info] [daemon] Starting Multipass 1.6.2+mac
[2021-03-05T09:23:36.969] [info] [daemon] Daemon arguments: /Library/Application Support/com.canonical.multipass/bin/multipassd --verbosity debug
[2021-03-05T09:23:37.996] [debug] [update] Latest Multipass release available is version 1.6.2

Launched: primary
Mounted '/Users/cibot' into 'primary:Home'

Name State IPv4 Image
primary Running 192.168.64.2 Ubuntu 20.04 LTS
```

Reproduce on macOS using the curl, installer, and multipass command sequence, with a deliberately slow startup or network. Start by tracing daemon startup and image discovery, then verify the behavior across the documented sequence; done means a fresh install does not report “No images found” or an unreachable remote during startup.

Written by the indexing model from the issue text.