Fix Locks

- Wrong return of lock releasing with DBA provider
- It's not possible to maintain Semaphore locks, since they aren't accessible by other processes
Should solve https://github.com/friendica/friendica/issues/7298#issuecomment-521996540

tests/src/Core/Lock/LockTest.php

@@ -190,4 +190,13 @@ abstract class LockTest extends MockedTest
 		$this->assertFalse($this->instance->isLocked('foo'));
 		$this->assertFalse($this->instance->isLocked('bar'));
 	}
+
+	/**
+	 * Test if releasing a non-existing lock doesn't throw errors
+	 */
+	public function testReleaseLockWithoutLock()
+	{
+		$this->assertFalse($this->instance->isLocked('wrongLock'));
+		$this->assertFalse($this->instance->releaseLock('wrongLock'));
+	}
 }