[Pandora] Fix coroutine scope/lifetime issues

Some glitchy utils mean that we can leak tasks beyond the scope of the
request handler. Ideally we should move the globalScope into Utils.kt so
it's not exposed to users at all.

Bug: 244782047
Tag: #stability
Test: atest pts-bot
Change-Id: I6e3b9f0b7b3faac48739a11caf3f0587c99dd3e5