Create task-runner container backups directory to avoid errors from tar
What does this MR do?
When running backup-utility --skip repositories --skip db --skip registry --skip external_diffs --skip terraform_state --skip uploads we will encounter error that [Error] tar (child): /srv/gitlab/tmp/backups/lfs.tar.gz: Cannot open: No such file or directory as /srv/gitlab/tmp/backups/ directory does not exist in the task runner container, therefore we need to create this directly when container is created.
Related issues
Closes #2233 (closed)
See Definition of done.
For anything in this list which will not be completed, please provide a reason in the MR discussion.
Required
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Merge Request Title and Description are up to date, accurate, and descriptive  - 
MR targeting the appropriate branch  - 
MR has a green pipeline on GitLab.com  
Expected (please provide an explanation if not completing)
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Test plan indicating conditions for success has been posted and passes  - 
Documentation created/updated  - 
Tests added  - 
Integration tests added to GitLab QA  - 
Equivalent MR/issue for omnibus-gitlab opened  
Edited  by Julius Kvedaras