[RootCanal] Clear links in rust LMP on timeout

We didn't do that initially, so the link count would steadily grow in
LMP until we ran out of slots.

Test: atest pts-bot
Bug: 239986609
Bug: 245578454
Tag: #stability
Ignore-AOSP-First: cherry-pick from AOSP
Change-Id: Ie387553f146817bbe58e94af7633cc36a80c3003
Merged-In: Ie387553f146817bbe58e94af7633cc36a80c3003