ULTs cleanup

- remove unused MemoryManagementFixture.
  MemoryLeaks are tracked using MemoryLeakListener no need to duplicate
  with Fixure.
  MMF should be used when you need to inject memory allocation failure

Change-Id: I95bcaa7051acf540c5b015c5489ed6a6fc38ee8e

unit_tests/os_interface/os_library_tests.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Intel Corporation
+ * Copyright (c) 2017 - 2018, Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -103,7 +103,6 @@ TEST_F(OSLibraryTest, testFailNew) {
 
         // Make sure that we only have 1 buffer allocated at a time
         delete library;
-        library = nullptr;
     };
     injectFailures(method);
 }