[6.14.z] duplicate bookmark negative test fix

[Satellite-QE]

Cherrypick of PR: #14232

Problem Statement

With SatelliteQE/airgun#1200 in, another problem uncovered in bookmarks. Trying to create a bookmark with already existing name doesn't raise exception in old style dialog (wontfix bz 1992652), it does so in the new style dialog (different one in stream than in 6.x runs). Affects ~20 tests

Solution

this pr attempts to cover all the cases

[Satellite-QE]

trigger: test-robottelo
pytest: tests/foreman/ui/test_bookmarks.py -k test_negative_create_with_duplicate_name

[Satellite-QE]

PRT Result

Build Number: 6141
Build Status: UNSTABLE
PRT Comment: pytest tests/foreman/ui/test_bookmarks.py -k test_negative_create_with_duplicate_name --external-logging
Test Result : = 7 failed, 29 passed, 1 skipped, 156 deselected, 125 warnings, 2 errors in 2586.70s (0:43:06) =

[pondrejk]

The failures pattern matches the master run, failures not related to changes from this PR (more investigation needed on the airgun side )