[common-utils] Fixes issue installing libssl3 on debian unstable

[pxslip]

Debian unstable has libssl3t64 installed, which conflicts with libssl3 and causes image creation to fail.

Added a test to pick libssl3t64 if available, falls back to libssl3 if not.

Some thoughts:

• Nesting ifs inside of the ^libssl3 test is unnecessary, but felt good for grouping the selection logic together.
• The elif fallback to libssl3 is likewise overly verbose, but I included it for readability. Changing to else should have the same outcome.

[pxslip]

@microsoft-github-policy-service agree