Wrong URI set for diagnostics of standalone java files

[fbricon]

When opening a standalone java file, we 1st link it to the default Java project in JDTUtils.getFakeCompilationUnit. The link is performed in a workspace job, but JDTUtils.getFakeCompilationUnit is already called within a IWorkspaceRunnable, in DocumentLifeCycleHandler.didOpen.
So by the time JDTUtils.getFakeCompilationUnit returns, the resource has not been actually linked yet, because the linking job hasn't run, which causes diagnostics to return the uri of the linked resource, not the one from the actual file