Fix displayName in phase.yml for community release job steps

[kiazhi]

PR Summary

fixes #107

• Update displayName
• Update the String after $(ImageName)- for the -TestLogPostfix parameter

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all Dockerfile, .sh, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.
• Adds a new image or tag
  • Not Applicable
• OR
  • Update README.powershell.md
  • Update README.powershellcommunity.md
  • Update vsts-ci.yml

[TravisEz13]

FYI, my last day in the office, until next year, will be tomorrow. So, don't expect much activity in the repo.

[kiazhi]

No worries. It's my last day of employment today and will be busy spending time looking for a new job for next year. I will continue with this repo some time next year because its holiday season for me too.

Have a great holiday break. Merry Christmas and Happy New Year. See you next year.

[TravisEz13]

Thanks for doing this. It's a great help. I also hoped it would help you get a little more familiar with the CI system.