servo: Merge #15696 - Do not pool HTTP connections (from jdm:no-http-pool); r=emilio

HTTP connection pooling triggers consistent failures in #14620. Let's disable it until there's more time to solve the underlying problem in #15694.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] There are tests for these changes

Source-Repo: https://github.com/servo/servo
Source-Revision: a780f6f28cf5d0f4faa7ad84822692d9bab1d031

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 0998c925cfb85a221d72a5043c16e19efd951365

servo/components/net/resource_thread.rs

@@ -325,7 +325,8 @@ impl CoreResourceManager {
             cookie_jar: group.cookie_jar.clone(),
             auth_cache: group.auth_cache.clone(),
             blocked_content: BLOCKED_CONTENT_RULES.clone(),
-            connector_pool: group.connector.clone(),
+            // FIXME(#15694): use group.connector.clone() instead.
+            connector_pool: create_http_connector("certs"),
         };
         let ua = self.user_agent.clone();
         let dc = self.devtools_chan.clone();