Audit switch location discovery logic for robustness in multi-rack deployments.

[internet-diglett]

omicron/sled-agent/src/rack_setup/service.rs

Lines 1324 to 1326 in 973bff1

	// Query MGS servers in each switch zone to determine which switch slot they are managing.
	// This logic does not handle an event where there are multiple racks. Is that ok?
	async fn map_switch_zone_addrs(

[bnaecker]

This code changed with #7779, but I believe it's still relevant.