osd: Torn write protection for Direct Reads

osd: Torn write protection for Direct Reads

It is possible for direct reads to query two seperate shards and
get different versions of the object for each shard when using
direct reads.

To solve this we add a get_internal_version op to tell us the version
of the object on that shard and submit that in the same transaction
as the read so we can ensure the versions are what we expect. If we
have a mismatch, we resubmit the read through the primary path.

Also a couple of spelling/tidy ups

Signed-off-by: Jon Bailey <jonathan.bailey1@ibm.com>
Signed-off-by: Alex Ainscow <aainscow@uk.ibm.com>
Signed-off-by: Callum James <callum.james@ibm.com>