common: include dirent.h to solve implicit declaration errors

Closes #1190
shell: Improve "Add VLAN" dialog.

By offering a default parent and ID and updating the default name as
the user types.

Fixes #1079
Closes #1174
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Correctly use the 'disabled' property to disable buttons.

And not 'disable', which has no effect.

Fixes #922
Closes #1197
Reviewed-by: Stef Walter <stefw@redhat.com>
Release version 0.24
shell: Correctly deal with asynchonicity on services page.

Make sure that the 'items' cache always corresponds to what is on the
page so that calls to update_service and update can be interleaved
arbitrarily.

Also don't try to use the manager after the page has been left.

Fixes #927
Fixes #1192