Ensure repeated connections are captured

std::map::emplace does not replace existing value if the key
already exists.

The newly constructed element will be destroyed immediately
if there already is an element with the key in the container.

Bug: 235872679
Bug: 232258524
Tag: #test
Test: gd/cert/run --sl4a --clean
Ignore-AOSP-First: cherry-pick

Merged-In: I340b723e805c0b94128bf6665690571f09dc9529
Change-Id: I340b723e805c0b94128bf6665690571f09dc9529
(cherry picked from commit 16b4e991)