Use absolute path for command replacements

[tunz]

Summary of the Pull Request

Onefuzz will replace command replacement values such as {input} to absolute paths instead of relative path.

PR Checklist

• Applies to work item: Full path of the input file #18
• CLA signed. If not, go over here and sign the CLI.
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Info on Pull Request

this will get canonicalized paths when they are evaluated. @bmc-msft this is what I described. This also handles the case that target_options has {input} well.

Validation Steps Performed

Updated test_expand testcase.