Fix first tests might be executed before ITR was properly evaluated

Author: Nacho Bonafonte

Sources/DatadogSDKTesting/DDTestObserver.swift

@@ -52,10 +52,11 @@ class DDTestObserver: NSObject, XCTestObservation {
             return
         }
 
+        Log.measure(name: "waiting itrWorkQueue") {
+            DDTestMonitor.instance?.itrWorkQueue.waitUntilAllOperationsAreFinished()
+        }
+
         if let itr = DDTestMonitor.instance?.itr {
-            Log.measure(name: "waiting itrWorkQueue") {
-                DDTestMonitor.instance?.itrWorkQueue.waitUntilAllOperationsAreFinished()
-            }
             let skippableTests = itr.skippableTests.filter { $0.suite == testSuite.name }.map { "-[\(testSuite.name) \($0.name)]" }
             let finalTests = tests.filter { !skippableTests.contains(($0 as AnyObject).name) }
             testSuite.setValue(finalTests, forKey: "_mutableTests")