lavf: Reset global flag on deinit

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -4136,6 +4136,7 @@ int avformat_network_deinit(void)
 #if CONFIG_NETWORK
     ff_network_close();
     ff_tls_deinit();
+    ff_network_inited_globally = 0;
 #endif
     return 0;
 }