Fix files not being highlighted if directory of file is already open

Summary:
In DolphinTabWidget::openFiles it assumes openDirectories will open new tabs, so it
only marks the URL selection for the newly opened tabs. This assumption is incorrect
 as Dolphin might reuse tabs when the folder is already open.

Even then, markUrlsAsSelected does nothing when the folder is already opened.
The selection seems to only be used when the folder finishes loading, calls made after
that only change a variable without updating the actual selection.

A call to DolphinView::updateViewState() is required to restore the intended behaviour, so long as DolphinView::clearSelection() has been called on the relevant tab, otherwise updateViewState() is a no-op.

BUG: 417230
FIXED-IN: 19.12.3

Test Plan:
1. In any application that has an "open containing folder" select that option
2. and then do the same for another file in the same folder

Reviewers: broulik

Reviewed By: broulik

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D27389