Replace Global Mutation in UKy Scaling

[MarcusHolly]

Summary/Motivation:

Addresses a comment raised by Doug here: #260 (comment)
Status: Waiting on the next IDAES release

Changes proposed in this PR:

• Replaces the global mutation in the UKy flowsheet scaling routine

Reviewer's checklist / merge requirements:

• The head branch (i.e. the "source" of the changes) is not the main branch on the PR author's fork
• Documentation
• Tests
• Diagnostic tests for models

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[dallan-keylogic]

This PR will have to wait until the new IDAES release, because it relies on the new default scaling API contained therein.

[ksbeattie]

Needs idaes release.