avformat/tests/fifo_muxer: includes libavformat/network.h to define ETIMEDOUT for fate build.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 9c041a3cd50694af4472fd63496c9606bc1057d2)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
diff --git a/libavformat/tests/fifo_muxer.c b/libavformat/tests/fifo_muxer.c
index 413700e..e20bd6e 100644
--- a/libavformat/tests/fifo_muxer.c
+++ b/libavformat/tests/fifo_muxer.c
@@ -25,6 +25,7 @@
 #include "libavutil/avassert.h"
 #include "libavformat/avformat.h"
 #include "libavformat/url.h"
+#include "libavformat/network.h"
 
 #define MAX_TST_PACKETS 128
 #define SLEEPTIME_50_MS 50000