When Ulpfec recovers a packet, set |returned| flag earlier.

This avoids infinite recursion in case the recovered packet carries a
RED header.

BUG=chromium:754748

Review-Url: https://codereview.webrtc.org/3004553002
Cr-Original-Commit-Position: refs/heads/master@{#19525}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 41476e014c8364adc15b90238d54a8aef91d7f56
1 file changed