conf: remove redundant ()

I almost copied-and-pasted some redundant () into my new code,
and figured a general cleanup prereq patch would be better instead.

No semantic change.

* src/conf/domain_conf.c (virDomainLeaseDefParseXML)
(virDomainDiskDefParseXML, virDomainFSDefParseXML)
(virDomainActualNetDefParseXML, virDomainNetDefParseXML)
(virDomainGraphicsDefParseXML, virDomainVideoAccelDefParseXML)
(virDomainVideoDefParseXML, virDomainHostdevFind)
(virDomainControllerInsertPreAlloced, virDomainDefParseXML)
(virDomainObjParseXML, virDomainCpuSetFormat)
(virDomainCpuSetParse, virDomainDiskDefFormat)
(virDomainActualNetDefFormat, virDomainNetDefFormat)
(virDomainTimerDefFormat, virDomainGraphicsListenDefFormat)
(virDomainDefFormatInternal, virDomainNetGetActualHostdev)
(virDomainNetGetActualBandwidth, virDomainGraphicsGetListen):
Reduce extra ().