Fix server fieldset layout in Chrome

[birtles]

Run storybook and then compare http://localhost:9001/?selectedKind=Components%7CSyncSettingsPanel&selectedStory=up%20to%20date&full=0&addons=1&stories=1&panelRight=0&addonPanel=storybook%2Factions%2Factions-panel in Firefox and Chrome.

This is a bug in Chrome that will apparently by fixed in LayoutNG. Until then perhaps we should just stop using a <fieldset> or add some sort of wrapper element for this.

[birtles]

Might affect Edge too.