PHPLIB-431: Relax aggregate explain test for 4.2 servers

Author: jmikola

tests/Operation/AggregateFunctionalTest.php

@@ -190,7 +190,13 @@ public function testExplainOption()
         $results = iterator_to_array($operation->execute($this->getPrimaryServer()));
 
         $this->assertCount(1, $results);
-        $this->assertArrayHasKey('stages', $results[0]);
+
+        /* MongoDB 4.2 may optimize aggregate pipelines into queries, which can
+         * result in different explain output (see: SERVER-24860) */
+        $this->assertThat($results[0], $this->logicalOr(
+            $this->arrayHasKey('stages'),
+            $this->arrayHasKey('queryPlanner')
+        ));
     }
 
     public function testExplainOptionWithWriteConcern()