storcon: don't assume host:port format in storcon client (#10347)

## Problem

https://github.com/neondatabase/infra/pull/2725 updated the scrubber to
use a non-host
port endpoint for storcon. That breaks when unwrapping the port.

## Summary of changes

Support both `host:port` and `host` formats for the storcon api.

storage_controller/client/src/control_api.rs

@@ -1,7 +1,6 @@
 use pageserver_client::mgmt_api::{self, ResponseErrorMessageExt};
 use reqwest::{Method, Url};
 use serde::{de::DeserializeOwned, Serialize};
-use std::str::FromStr;
 
 pub struct Client {
     base_url: Url,
@@ -31,16 +30,11 @@ impl Client {
         RQ: Serialize + Sized,
         RS: DeserializeOwned + Sized,
     {
-        // The configured URL has the /upcall path prefix for pageservers to use: we will strip that out
-        // for general purpose API access.
-        let url = Url::from_str(&format!(
-            "http://{}:{}/{path}",
-            self.base_url.host_str().unwrap(),
-            self.base_url.port().unwrap()
-        ))
-        .unwrap();
-
-        let mut builder = self.client.request(method, url);
+        let request_path = self
+            .base_url
+            .join(&path)
+            .expect("Failed to build request path");
+        let mut builder = self.client.request(method, request_path);
         if let Some(body) = body {
             builder = builder.json(&body)
         }