virsh: Create macro for "file" option
virsh: Create macro for "file" option

Rather than continually cut/paste the "file" option for pool command
option structures, generate a macro which will commonly define it for
any command.  Then of course use that macro.

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