Update Docker push commands and add checks for App properties

[Phydeauxman]

Description

Updated the commands used to push Docker image to use dynamic endpoints.
Added login to wait for the App creation process to propagate all properties before proceeding

Issue reference

The issue this PR will close: #144

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles or validates correctly
• BASH scripts have been validated using shellcheck
• All tests pass (manual and automated)
• The documentation is updated to cover any new or changed features
• Markdown files have been linted using the recommended linter. (See .vscode/extensions.json.)
• Relevant issues are linked to this PR

[glennmusa]

We still have work to do to pass along the Key Vault DNS suffix and the ARM metadatahost endpoint URL from the results of az cloud show but let's do that in another change. LGTM 👍