[NTOS]: Improve a bit CmpDeepCopyKeyInternal():

[NTOS]: Improve a bit CmpDeepCopyKeyInternal():
- Normally getting the SrcNode and DestNode must succeed (checked with assert);
- Set the DestNode Flags member, in particular when this is the new root node of the saved registry hive;
- Copy the key class cell (OK), and the key security cell (currently done in a hackish way; proper way: call the CmpAssignSecurity* function);
- Add more clean-up on failure;
- Warn in code about the fact that CmpDeepCopyKeyInternal is recursive, and will easily exhaust kernel stack. This function will need to be reworked later...
CORE-10793 CORE-10796

svn path=/trunk/; revision=75171