Make sure we don't resize clients before they've been set up

Summary:
On Placement=Maximized it becomes a problem because we end up sending an invalid size and when we try to recover from it, we recover from the wrong size.
This fixes setting the right size to Plasma Mobile applications.

Reviewers: #kwin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D22054