virDomainObjList: Introduce yet another hash table

virDomainObjList: Introduce yet another hash table

This hash table will contain the same data as already existing one.
The only difference is that while the first table uses domain uuid as
key, the new table uses domain name. This will allow much faster (and
lockless) lookups by domain name.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>