fix: more aggressively cleanup storage accounts during VHD builds

[cameronmeissner]

… cleanup

What type of PR is this?

What this PR does / why we need it:

we now always cleanup storage accounts regardless of dry run or not, and more aggressively delete anything older than 12 hours - this is to address storage account quota issues in ACS test causing VHD build failures

Which issue(s) this PR fixes:

Fixes #

Requirements:

• [ ] uses conventional commit messages
• [ ] includes documentation
• [ ] adds unit tests
• [ ] tested upgrade from previous version

Special notes for your reviewer:

Release note:

none

[coveralls]

Pull Request Test Coverage Report for Build 8602684839

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.077%

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Totals
Change from base Build 8587693813:	0.0%
Covered Lines:	2450
Relevant Lines:	2985

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💛 - Coveralls

[cameronmeissner]

@AbelHu @junjiezhang1997