Fix receiving data over the unix socket

Don't use MSG_WAITALL since we can (and often will) receive less data
than MTU with the new IPC.
diff --git a/audio/unix.c b/audio/unix.c
index ed7df0b..d43f4d7 100644
--- a/audio/unix.c
+++ b/audio/unix.c
@@ -1117,7 +1117,7 @@
 
 	memset(buf, 0, sizeof(buf));
 
-	len = recv(client->sock, buf, sizeof(buf), MSG_WAITALL);
+	len = recv(client->sock, buf, sizeof(buf), 0);
 	if (len < 0) {
 		error("recv: %s (%d)", strerror(errno), errno);
 		goto failed;