storage: Use virStoragePoolObjGetDef accessor for new driver events
storage: Use virStoragePoolObjGetDef accessor for new driver events

Missed from merge from commit id 'b0652192' into commit id 'bfcd8fc92'
were a couple of obj->def-> references.

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