Added checkExist on error in step upload/postFile + Added getVersions check in step activateVersion

[TimKara]

This fix is to fix the following bug/error:
Error: An error occured. Try running the command again with -D,--debug flag. { res: undefined, err: Error: SSL Error: ERR_TLS_CERT_ALTNAME_INVALID at Request.onRequestResponse (C:\Development\Source\GIT\*******\build\node_modules\request\request.js:948:24)

[salesforce-cla]

Thanks for the contribution! Unfortunately we can't verify the commit author(s): Tim Kara <t***@A***.dk>. One possible solution is to add that email to your GitHub account. Alternatively you can change your commits to another email and force push the change. After getting your commits associated with your GitHub account, sign the Salesforce.com Contributor License Agreement and this Pull Request will be revalidated.

[tobiaslohr]

Thanks for contributing @TimKara! Can you please have a look at the conflicts and resolve. Also there are some tests failing:

> sfcc-ci@2.6.0 test
> npm run lint && npm run test:unit


> sfcc-ci@2.6.0 lint
> eslint --ignore-path .gitignore ./


/home/circleci/project/lib/code.js
  132:1   error  Line 132 exceeds the maximum line length of 120  max-len
  133:13  error  Expected space(s) after "if"                     keyword-spacing
  136:20  error  Expected space(s) after "if"                     keyword-spacing
  423:13  error  Expected space(s) after "if"                     keyword-spacing
  427:25  error  Expected space(s) after "if"                     keyword-spacing

✖ 5 problems (5 errors, 0 warnings)
  4 errors and 0 warnings potentially fixable with the `--fix` option.

[tobiaslohr]

Hi @TimKara , following up here to see, if you can check the conflicts and also resolve #186 (comment).

Thanks!