Include DrupalApcCache::deleteKeys() and DrupalApcCache::deleteKey() to the logged operations (instead of DrupalApcCache::clear())

To understand what happens with the cache items, and why some items are missing, it is important that DrupalApcCache::deleteKeys() and DrupalApcCache::deleteKey() are logged as operations done on the cache.

Since those methods are called from DrupalApcCache::clear(), this method should not be longer logged.