conf: Add missing apostrophe to error message
conf: Add missing apostrophe to error message

Signed-off-by: Luyao Huang <23d9981432efa88691fd2a71f5525bc2174f7664@redhat.com>

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