friendica-5847 Console Cache List command doesn't work

- Added $prefix to all CacheDriver
- Moved hostname magic to CacheDriver
- Added test for getAllKeys()

tests/src/Core/Cache/MemcacheCacheDriverTest.php

@@ -11,11 +11,6 @@ use Friendica\Core\Cache\CacheDriverFactory;
  */
 class MemcacheCacheDriverTest extends MemoryCacheTest
 {
-	/**
-	 * @var \Friendica\Core\Cache\IMemoryCacheDriver
-	 */
-	private $cache;
-
 	protected function getInstance()
 	{
 		$this->cache = CacheDriverFactory::create('memcache');