virtualizationservice: clean up

This is a follow up of 21e9b928ef7683ecbfc6fff17a5b588c791d385a and
adfb76c3cf021ae645341e94f8e85ac46d6791ec.

* fix typo
* use more rusty style
* add more comments

Bug: n/a
Test: MicrodroidHostTestCases
Change-Id: I1e763defa062eb61e243438542893f0046165366
8 files changed