legacy stats: update timestamp on localcandidate/remotecandidate
legacy stats: update timestamp on localcandidate/remotecandidate

updates the timestamp on the local and remote candidate stats for consistency
with other places. This also makes the graphs on chrome://webrtc-internals
work (even though most values don't update so showing graphs is not meaningful)

BUG=chromium:937833

Change-Id: I3267dd7a5f5a887dcd0756137077b8f02c201905
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128765
Reviewed-by: Henrik Boström <106ab6647ddadbf38d6259e9d5ec4de77fa52c00@webrtc.org>
Reviewed-by: Steve Anton <93f73658da16553b94c040887a439a155812e54e@webrtc.org>
Commit-Queue: Steve Anton <93f73658da16553b94c040887a439a155812e54e@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#27248}
ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc