[Ingest Manager] Fix limited concurrency helper (#73976) (#73994)

Author: nchaulet

x-pack/plugins/ingest_manager/server/routes/limited_concurrency.test.ts

@@ -39,7 +39,7 @@ describe('registerLimitedConcurrencyRoutes', () => {
 });
 
 // assertions for calls to .decrease are commented out because it's called on the
-// "req.events.aborted$ observable (which) will never emit from a mocked request in a jest unit test environment"
+// "req.events.completed$ observable (which) will never emit from a mocked request in a jest unit test environment"
 // https://github.com/elastic/kibana/pull/72338#issuecomment-661908791
 describe('preAuthHandler', () => {
   test(`ignores routes when !isMatch`, async () => {

x-pack/plugins/ingest_manager/server/routes/limited_concurrency.ts

@@ -66,9 +66,7 @@ export function createLimitedPreAuthHandler({
 
     maxCounter.increase();
 
-    // requests.events.aborted$ has a bug (but has test which explicitly verifies) where it's fired even when the request completes
-    // https://github.com/elastic/kibana/pull/70495#issuecomment-656288766
-    request.events.aborted$.toPromise().then(() => {
+    request.events.completed$.toPromise().then(() => {
       maxCounter.decrease();
     });