cli: fix problem restarting tunnel with uppercase letter in name (microsoft#180881)

Fixes microsoft#180693

Author: connor4312

cli/src/tunnels/dev_tunnels.rs

@@ -384,10 +384,11 @@ impl DevTunnels {
 	) -> Result<ActiveTunnel, AnyError> {
 		let (mut tunnel, persisted) = match self.launcher_tunnel.load() {
 			Some(mut persisted) => {
-				let as_lowercase = persisted.name.to_ascii_lowercase();
-				let preferred_name = preferred_name.unwrap_or(&as_lowercase);
-				if persisted.name != preferred_name {
-					(_, persisted) = self.update_tunnel_name(persisted, preferred_name).await?;
+				if let Some(preferred_name) = preferred_name.map(|n| n.to_ascii_lowercase()) {
+					if persisted.name.to_ascii_lowercase() != preferred_name {
+						(_, persisted) =
+							self.update_tunnel_name(persisted, &preferred_name).await?;
+					}
 				}
 
 				let (tunnel, persisted, _) = self