Add image support for DOD Platform One flavor

[nmnellis]

I would like the ability to use getIstio to deploy images from IronBank offered by the Department of Defense listed here

https://registry1.dso.mil/harbor/projects/3/repositories/opensource%2Fistio%2Fproxyv2 https://registry1.dso.mil/harbor/projects/3/repositories/opensource%2Fistio%2Foperator https://registry1.dso.mil/harbor/projects/3/repositories/opensource%2Fistio%2Fpilot https://registry1.dso.mil/harbor/projects/3/repositories/opensource%2Fistio-1.8%2Fistioctl

It does require docker login credentials but it is free to sign up.

[sfc-gh-dwu]

+1 and are the fips builds also available via IronBank?

[sbko]

@sfc-gh-dwu FIPS images aren't available via IronBank, at least at this point in time. @nmnellis What is the use case of having IronBank images in getmesh? Are you using BigBang?