commitlog: align input of dma_write() during segment recycle
commitlog: align input of dma_write() during segment recycle

Normally a file size should be aligned around block size, since
we never write to it any unaligned size. However, we're not
protected against partial writes.

Just to be safe, align up the amount of bytes to zerofill
when recycling a segment.

Message-Id: <b0b67d14411548e5a3bb8617b9b3cafc545ab2e3@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla