fusefronted: more concise corrupt block log message
fusefronted: more concise corrupt block log message

Calculating the block offset is easy enough, even more now
that gocryptfs-xray exists.

rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs,davesteele/gocryptfs,davesteele/gocryptfs,davesteele/gocryptfs,rfjakob/gocryptfs