qemu: Resolve Coverity DEADCODE.
qemu: Resolve Coverity DEADCODE.

reported here: http://www.redhat.com/archives/libvir-list/2014-November/msg00327.html

I could have just remove bool supportMaxOptions variable, but
if I had do this, we could not check anymore if the nparams variable is
superior to QEMU_NB_BLOCK_IO_TUNE_PARAM_MAX.

v2: change following this proposal:
http://www.redhat.com/archives/libvir-list/2014-November/msg00379.html

VenkatDatta/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,olafhering/libvirt,datto/libvirt,shugaoye/libvirt,zippy2/libvirt,elmarco/libvirt,rlaager/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,zippy2/libvirt,elmarco/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,rlaager/libvirt,crobinso/libvirt,datto/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,rlaager/libvirt,nertpinx/libvirt,taget/libvirt,andreabolognani/libvirt,eskultety/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,crobinso/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,taget/libvirt,zippy2/libvirt,elmarco/libvirt,eskultety/libvirt,shugaoye/libvirt,agx/libvirt,jardasgit/libvirt,libvirt/libvirt,olafhering/libvirt,rlaager/libvirt,andreabolognani/libvirt,jfehlig/libvirt,elmarco/libvirt,andreabolognani/libvirt,taget/libvirt,libvirt/libvirt,eskultety/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,eskultety/libvirt,jardasgit/libvirt,taget/libvirt,taget/libvirt,elmarco/libvirt,datto/libvirt,nertpinx/libvirt,agx/libvirt,libvirt/libvirt,crobinso/libvirt,agx/libvirt,crobinso/libvirt,jardasgit/libvirt,zippy2/libvirt,rlaager/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,eskultety/libvirt,datto/libvirt,nertpinx/libvirt,jfehlig/libvirt,shugaoye/libvirt,agx/libvirt,jardasgit/libvirt,datto/libvirt,agx/libvirt,nertpinx/libvirt