[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.

Tag: #stability
Bug: 245578454
Test: Test: atest pts-bot
Ignore-AOSP-First: Cherry-pick from aosp
Merged-In: I6e3b9f0b7b3faac48739a11caf3f0587c99dd3e5
Change-Id: I6e3b9f0b7b3faac48739a11caf3f0587c99dd3e5