Unit Test - gitreader.go

Add unit tests to validate methods under utils package which are defined in [gitreader.go](https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/utils/gitreader.go)

All unit tests should go in gitreader_test.go under [utils/](https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/utils)

```
func NewGitReader(projectName string, record DependencyRecord) *GitReader {
...
}

func (reader *GitReader) CloneDependency() error {
...
}
```

Start by reading utils/gitreader.go, focusing on NewGitReader and GitReader.CloneDependency. Add the unit tests to utils/gitreader_test.go and run the utils package tests. The work is done when both named methods have tests that validate their behavior.

Written by the indexing model from the issue text.