CLI-1370: PHP warning in pull:db when backup fails

[danepowell]

Motivation

Fixes warnings when a backup (or any other Cloud API task) fails

Proposed changes

Check the notification response to make sure the task completed successfully

Testing steps

1. Follow the contribution guide to set up your development environment or download a pre-built acli.phar for this PR.
2. Clear the kernel cache to pick up new and changed commands: ./bin/acli ckc
3. (add specific steps for this pr)

[codecov]

Codecov Report

Attention: Patch coverage is 94.11765% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.02%. Comparing base (938f87b) to head (a6bfa06).

Files	Patch %	Lines
src/Command/Env/EnvMirrorCommand.php	87.50%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1776      +/-   ##
============================================
- Coverage     92.02%   92.02%   -0.01%     
- Complexity     1819     1826       +7     
============================================
  Files           121      121              
  Lines          6838     6844       +6     
============================================
+ Hits           6293     6298       +5     
- Misses          545      546       +1     

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[github-actions]

Try the dev build for this PR: https://acquia-cli.s3.amazonaws.com/build/pr/1776/acli.phar

curl -OL https://acquia-cli.s3.amazonaws.com/build/pr/1776/acli.phar
chmod +x acli.phar