Add error assertion for files/FindUpstream chdir functions

[sverdlov93]

Is your feature request related to a problem? Please describe.

Add error assertion for findUpstream() chdir functions. Simple assert ( if err != nil ... ) won't be enough, the logic should be changed.

Same on GetProjectRoot()

[SteveNewson]

This is probably fixed by https://github.com/jfrog/jfrog-client-go/pull/537

However, the nebulous comment "the logic should be changed" may mean that there should be some further enhancements which have not been considered.