Live searchbox shows with scroll bars on Users/Groups panel

[mauritsvanrees]

On the Users and Groups control panel, both the Users tab and the Groups tab, the live searchbox needlessly shows with scroll bars:

This is caused by commit d006020, which has been there since Plone 5.0.0, and is still there in 5.1.2 (or current coredev 5.0 and 5.1).
Best solution is probably to make the css identifier more specific: only set the overflow on forms within the id content-core.

Additionally, this may be useful, to make the remaining users/groups form prettier:

• Set overflow to auto, because currently the scroll bars show even when no scroll bar is needed.
• Only set overflow-x, because I don't think we mind that the list is long vertically. We only care about the horizontal overflow, because it may disappear behind a portlet (User and Groups controlpanel unusable when using more roles Products.CMFPlone#879).

[vincentfretin]

Actually it's worse, look at the livesearch in Plone 5.2.2rc1

[vincentfretin]

Same issue on the Add new user modal.