Hide groups by default when initialising

This ensures that when the status pipe is first output that only active groups
are output, rather than all groups, due to the presence of the gc->hidden flag
being set for groups with clients (c.f. clients being recaptured on restart).
Update status info after EWMH wrangling

Output the status information for active group, after the EWMH stuff.  No
functional change here, just feels neater.