Move the simulator-side RezAttachments call on login to SP.MakeRootAgent with the other attachments code, using TeleportFlags.ViaLogin check to fire if necessary.

This is to simplify the code (no tricky 'wasChild' signalling required)
and to reduce the risk of a thread clash between simulator-side attaching (necessary for v1 viewers)
and the viewer-side attaching the v3 viewers perform.
Merge branch 'master' of ssh://opensimulator.org/var/git/opensim