xenconfig: rm format/parse multi serial for xen-xm
xenconfig: rm format/parse multi serial for xen-xm

xen-xm doesn't support multi serial at all, this patch drop the
domXML <-> xl.cfg conversions.

Signed-off-by: Bob Liu <f1431bf4ea962ea2009f7275289c2e0b23d8aceb@oracle.com>

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