- Fix registry lock leakages in CmpDoOpen in failure cases.

- Fix registry lock leakages in CmpDoOpen in failure cases.
- Add support for a special case of opening existing (cached) KCBs by CmpDoOpen.
- Specify a flag for that case in one specific case inside CmpParseKey, which allows us to get rid of the "\\REGISTRY" hack inside the code, fixes the 'Kcb->RefCount == 1' assertion failure, and certainly fixes registry-related regression tests. There might be some side effects in theory, but since this hack only applied to the root key, they shouldn't happen. Thanks to Stefan for helping in debugging and a testcase.

svn path=/trunk/; revision=38272