commit log reader bugfix: Fix tried to read entries across chunk bounds
commit log reader bugfix: Fix tried to read entries across chunk bounds

read_entry did not verify that current chunk has enough data left
for a minimal entry. Thus we could try to read an entry from the slack
left in a chunk, and get lost in the file (pos > next, skip very much
-> eof). And also give false errors about corruption.

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