Don't store view properties on network shares

Entering a folder will have Dolphin determine whether it can store the view properties in a .directory file within the folder or
in a generic config location.
It does so by checking for permissions on the file and parent dir causing various stat calls that potentially block on a slow mount.
Also, the config reading thereafter can be very slow.
Moreover, network shares are typically shared between users, so one user's view properties shouldn't affect or be overwritten
by this Dolphin instance.
It doesn't resolve symlinks but is surely an improvement over the status quo.

Differential Revision: https://phabricator.kde.org/D23458

src/views/viewproperties.cpp

@@ -26,6 +26,8 @@
 
 #include <QCryptographicHash>
 
+#include <KFileItem>
+
 namespace {
     const int AdditionalInfoViewPropertiesVersion = 1;
     const int NameRolePropertiesVersion = 2;
@@ -70,6 +72,11 @@ ViewProperties::ViewProperties(const QUrl& url) :
         m_filePath = url.toLocalFile();
 
         bool useDestinationDir = !isPartOfHome(m_filePath);
+        if (!useDestinationDir) {
+            const KFileItem fileItem(url);
+            useDestinationDir = fileItem.isSlow();
+        }
+
         if (!useDestinationDir) {
             const QFileInfo dirInfo(m_filePath);
             const QFileInfo fileInfo(m_filePath + QDir::separator() + ViewPropertiesFileName);