Refactor boxslotcyl advection test to use icepack parameters

[phil-blain]

PR checklist

• Short (1 sentence) summary of your PR:
  After I did Advection test - slotted cylinder #254, I realized that two constants I had defined actually already existed in icepack_parameters. I updated the code to use them to reduce duplication.
• Developer(s):
  Philippe Blain
• Suggest PR reviewers from list in the column to the right. @eclare108213
• Please copy the PR test results link or provide a summary of testing completed below.
  base_suite results:

214 of 214 tests PASSED
0 of 214 tests FAILED
0 of 214 tests PENDING

• How much do the PR code changes differ from the unmodified code?
  • bit for bit
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
  • Yes (Is this what is meant here ? )
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please provide any additional information or relevant details below:

[phil-blain]

UCAR FTP is down...

[eclare108213]

Good catch. Instead of making days_to_s a pointer to secday, please use secday directly. Thanks!

[eclare108213]

Travis is failing on the NCAR ftp. Did the filenames change with the new JRA55 data?

[apcraig]

Travis should be working. Sometimes, the wget fails (for reasons I don't understand). Usually if you trigger the build again, it works on the 2nd or 3rd try. It looks like someone just triggered the build again.

[apcraig]

This can probably be merged straight-away. @eclare108213 feel free to do that after you've had another look. Travis worked on 2nd attempt.

[mattdturner]

Sometimes, the wget fails (for reasons I don't understand)

Travis has issues with FTP.

the FTP protocol cannot be reliably used on our sudo-enabled Linux hosted infrastructure anymore.
Source: https://blog.travis-ci.com/2018-07-23-the-tale-of-ftp-at-travis-ci

I know our .travis.yml file has sudo: false included, but that doesn't seem to resolve the issue. It is suggested to use wget with http(s), or sftp to download the files. I'm not sure if that is an option on the NCAR FTP.