Add more unit tests

[cmainas]

For the time being we have a few unit tests in urunc. However, these are too less and we need to add a lot more and cover as much code as possible.

[parthdagia05]

Hi @cmainas I'd like to start contributing here. I'd like to add unit tests for pkg/unikontainers/hypervisors/utils.go. It currently has no test coverage.