storage XML to libvirtd, which was saved in /etc/libvirt/storage.  On subsequent
stop/start of libvirtd, because of another bug , an
error wasn't being set properly in an error path, so libvirtd was SEGV'ing in
storage_conf.c:virStoragePoolObjLoad when trying to dereference the NULL err
returned from virGetLastError().  Make this more robust against errors by always
doing "err ? err->message : NULL" in the printf.  I looked around the tree and
found a couple of other places that weren't guarded, so this patch fixes them as
well.
Signed-off-by: NChris Lalancette <clalance@redhat.com>