be robust against broken summary files
be robust against broken summary files

Now that we can boot without a Summary file, we can just as easily boot
with a broken one.

Suggested by Nadav, and it is actually very easy to do, so do it.

Signed-off-by: Glauber Costa <7ba9037b0dd006f9408bd45b94707becd5cd4e87@scylladb.com>

duarten/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,duarten/scylla,raphaelsc/scylla,kjniemi/scylla,raphaelsc/scylla,kjniemi/scylla,kjniemi/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,duarten/scylla,raphaelsc/scylla,scylladb/scylla