UI: Add more descriptive message upon submitting invalid credentials

[ilija-lazoroski]

Issue: #3942

What does this PR do?

Fixes #3942

Add any further explanations here.

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?
• Have you checked that you haven't introduced any duplicate code?

Testing Checklist

• Added relevant unit tests?
• Do all unit tests pass?
• Do all end-to-end tests pass?
• Any other testing performed?

  Tested by {Running the Monkey locally with relevant config/running Island/...}

• If applicable, add screenshots or log transcripts of the feature working

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4fe4bed) 77.57% compared to head (86bebfe) 77.57%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3977   +/-   ##
========================================
  Coverage    77.57%   77.57%           
========================================
  Files          467      467           
  Lines        14759    14759           
========================================
  Hits         11450    11450           
  Misses        3309     3309           

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[mssalvatore]

Approved, but it might be worth rolling up identical messages. E.g. ("3 invalid NTLM hashes were found")