Add unit tests for file sync code

[johnmcollier]

While implementing #2626, I saw that our file sync code (CopyFile() and the functions it depends on) didn't have any unit test coverage and only our integration tests were providing test coverage.

As this is such a critical piece of code for one of odo's core functionalities, we should add unit tests to it and ensure that there is proper test coverage

• Figure out if we can test sync.CopyFile with the mock Kube API
  • This might be tricky as it requires an already running pod to exec to, and I'm not sure if the test/mock Kube API can handle that
• Add unit tests for checkFileExist, makeTar and recursiveTar functions
  • These should be relatively straightforward to test and don't depend on the Kube API.

/area testing

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[openshift-bot]

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/lifecycle stale

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[openshift-ci-robot]

@openshift-bot: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity.

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