Fix dockerhub build hook

[zbeekman]

• Extra/erroneous tags were being inserted when run on dockerhub infra

coverage on master

Summary of changes

Dockerhub build hook (script)

Rationale for changes

So that pushes to master will build the docker image and that can be used to launch a jupyter-CAF-kernel binder notebook based on the master branch.

Additional info and certifications

This pull request (PR) is a:

• Bug fix
• Feature addition
• Other, Please describe:

I certify that

• I certify that:
  • I have reviewed and followed the contributing guidelines
  • I will wait at least 24 hours before self-approving the PR to give another
    OpenCoarrays developer a chance to review my proposed code
  • I have not introduced errant white space (no trailing white space or white space errors may
    be introduced)
  • I have added an explanation of what these changes do and why they should be included
  • I have checked to ensure there aren't other open Pull Requests for the same change
  • I have you written new tests for these changes
  • I have successfully tested these changes locally
  • I have commented any non-trivial, non-obvious code changes
  • The commits are logically atomic, self consistent and coherent
  • The commit messages follow best practices
  • Test coverage is maintained or increased after this is merged

Code coverage data

[codecov]

Codecov Report

Merging #650 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #650   +/-   ##
=======================================
  Coverage   53.02%   53.02%           
=======================================
  Files           3        3           
  Lines        2863     2863           
=======================================
  Hits         1518     1518           
  Misses       1345     1345