Upgraded dotnet 2.0 references to 2.1 mcr references

[Nickomang]

Purpose

• To avoid docker throttling unauthenticated pulls, we've moved images previously hosted on dockerhub at microsoft/* to an MCR equivalent. This PR DOES include an upgrade of Dotnet Core 2.0 references to 2.1. Please do not merge this PR until testing has been done to ensure no breaking changes.

Does this introduce a breaking change?

[ ] Yes
[ ] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[x] Other... Please describe: Addresses the impending issue of docker throttling unauthenticated pulls

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information