[misc] Make MockitoOldCore XWiki instane a spy instead of a mock

...tension/xar/internal/handler/XarExtensionHandlerTest.java

...r/instance/internal/AbstractInstanceFilterStreamTest.java

...ternal/output/DocumentInstanceOutputFilterStreamTest.java

...e/internal/output/UserInstanceOutputFilterStreamTest.java

.../org/xwiki/filter/test/xarinstance/XARToInstanceTest.java

.../test/it/org/xwiki/ldap/XWikiLDAPAuthServiceImplTest.java

...st/java/com/xpn/xwiki/web/XWikiMessageToolBridgeTest.java

...n/wiki/internal/DocumentTranslationBundleFactoryTest.java

...i-platform-oldcore/src/main/java/com/xpn/xwiki/XWiki.java

...test/java/com/xpn/xwiki/doc/XWikiDocumentMockitoTest.java

.../internal/objects/classes/XClassMigratorListenerTest.java

...t/java/com/xpn/xwiki/objects/classes/DBListClassTest.java

...va/com/xpn/xwiki/objects/classes/DBTreeListClassTest.java

...va/com/xpn/xwiki/objects/classes/StaticListClassTest.java

...rc/test/java/com/xpn/xwiki/store/XWikiCacheStoreTest.java

.../src/test/java/com/xpn/xwiki/test/MockitoOldcoreRule.java

...m/xpn/xwiki/user/impl/xwiki/XWikiAuthServiceImplTest.java

.../xpn/xwiki/user/impl/xwiki/XWikiGroupServiceImplTest.java

...e/src/test/java/com/xpn/xwiki/web/DownloadActionTest.java

...ore/src/test/java/com/xpn/xwiki/web/ExportActionTest.java