[2.4.x backport][Jupyter] Fix datums-related error message when notebooks starts up

[smalyala]

Make datums request at notebooks startup only when connected to a cluster and logged in if auth enabled (when mount server response is 200).

Ticket: https://linear.app/pachyderm/issue/INT-760/error-message-when-starting-up-notebooks

JIRA: INT-782

[codecov]

Codecov Report

Merging #8479 (5229825) into 2.4.x (5229825) will not change coverage.
The diff coverage is n/a.

❗ Current head 5229825 differs from pull request most recent head ce17d01. Consider uploading reports for the commit ce17d01 to get more accurate results

@@           Coverage Diff           @@
##            2.4.x    #8479   +/-   ##
=======================================
  Coverage   38.94%   38.94%           
=======================================
  Files         425      425           
  Lines      117494   117494           
=======================================
  Hits        45761    45761           
  Misses      62651    62651           
  Partials     9082     9082           

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more