Leases occasionally fail with a constraint violation

```
[02] 17:51:47 DBG Failed to acquire lease, will retry
error="/Users/alec/dev/zero/providers/leases/sql.go:213: /Users/alec/dev/zero/providers/sql/postgres.go:33: constraint violation: ERROR: duplicate key value violates unique constraint \"leases_pkey\" (SQLSTATE 23505)"
```

Update: this appears to be during hot reload, so is actually probably the correct behaviour. It probably hot reloaded while the lease was held and has to wait for it to expire.