Fix build by dropping redefined typedefs

Fix build by dropping redefined typedefs

Commit 93e82727 introduced numatune_conf.h file that contains
typedefs already defined in domain_conf.h, such as:

 - virDomainNumatune
 - virDomainNumatunePtr
 - virDomainDef
 - virDomainDefPtr

As numatune_conf.h is included by domain_conf.h, clang
complains about redefinition of typedef and the build fails.

In order to fix it, drop typedefs already defined by numatume_conf.h
from domain_conf.h.