Improve test coverage of //pkg/runtime

[douglas-reid]

https://codecov.io/gh/istio/mixer/tree/master/pkg/runtime

There are some files in this package that should be fairly easy for which to improve coverage:

• env.go
• init.go
• logger.go
• resourceType.go

[jmuk]

Seems to be solved by @mandarjog https://github.com/istio/mixer/pull/1300? I don't know why codecov isn't refreshed yet, but env.go, logger.go, and resourceType.go are now 100% covered. init.go is low, but I think it's by-design.

[sakshigoel12]

@douglas-reid can you update release milestone