input/InputStreams: pass std::unique_lock<> to various methods

src/command/FileCommands.cxx

@@ -292,9 +292,9 @@ read_stream_art(Response &r, const char *uri, size_t offset)
 	size_t read_size;
 
 	{
-		const std::lock_guard<Mutex> protect(mutex);
-		is->Seek(offset);
-		read_size = is->Read(&buffer, CHUNK_SIZE);
+		std::unique_lock<Mutex> lock(mutex);
+		is->Seek(lock, offset);
+		read_size = is->Read(lock, &buffer, CHUNK_SIZE);
 	}
 
 	r.Format("size: %" PRIoffset "\n"

src/command/FingerprintCommands.cxx

@@ -305,7 +305,7 @@ GetChromaprintCommand::Read(InputStream &is, void *buffer, size_t length)
 		cond.wait(lock);
 	}
 
-	return is.Read(buffer, length);
+	return is.Read(lock, buffer, length);
 }
 
 CommandResult