Guard tests against broken Gurobi licenses

[jsiirola]

Fixes # .

Summary/Motivation:

This resolves a number of tests that fail when Gurobi (or gurobipy is installed on the system, but the license is not currently valid (e.g., expired).

Changes proposed in this PR:

• Guard tests: skip when Gurobi is present but not licensed
• Simplify some import management in AOS

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.