Remove expensive logging call.

Remove expensive logging call in the vector clock computation code.
Ignore response.
Remove expensive comment.
Remove expensive logging call.
Remove unnecessary logging; don't block for response.

Remove logging calls which are not necessary and very expensive.  No
longer wait for downstream operation generation.
Remove timeouts.

Remove timeouts and logging messages which are expensive.
Remove instrumentation code.
Remove expensive logging messages.
Merge branch 'master' into downstreamop
Fix a bug: tx_coord did not send downstream op to clocksi_vnode
Add downstream generation to stx transaction