[6.15.z] host_new>content>errata tab pagination

[Satellite-QE]

Cherrypick of PR: #1152

Purpose

• supports robottelo #13767
• Add new host UI support for reading errata tab pagination.
• method could be extended to any content>{tab with pagination} in New Host UI page once working.

Solution

-Added new method clear() to SearchInput class (aigun/widgets.py)
-usage in the airgun view like soview.content.errata.searchbar.clear()
-Now using this in apply_erratas() method (entities/host_new.py), to clear the searchbar of any possible value present, when no search passed to apply_erratas(), meaning show and apply all errata with a blank searchbar.
-We also clear the searchbar in apply_erratas() after installing, that way any search value passed does not persist in the searchbar.

Issue, Resolved

• When reading info from PF4Pagination object in views/host_new.py@362, we get an empty dictionary with no information. Solved
• When the method apply_erratas(entity, search) is run, it will leave the searchbar filled, and keep it filled until the view is reset.
• Workaround: Before accessing view.content.errata.pagination, we pass ' ' to searchbar, to display all available errata unfiltered. In case the searchbar was left occupied by a method run previously. I have been looking for a better way or built in method to clear the searchbar /unfilter, before geting pagination.

[vsedmik]

trigger: test-robottelo
pytest: tests/foreman/ui/test_errata.py -k end_to_end

[vsedmik]

CP looks correct, PRT passed