Properly copy the UserScriptData

UserScriptControllerHost keeps a collection of UserScripts
and not the UserScriptData, which is a simple struct intended
to be passed over IPC. Rely on the compiler generated copy
constructor to copy that data.

Change-Id: Ib5479e634f10d3646a10b644b0eaee471e48f5b8
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>