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.
Merge branch 'origin/master'

Conflicts:
	src/clocksi_downstream_generator_vnode.erl
	src/vectorclock.erl
get stable snapshot time from a node
wait for vetorsnapshot time
Use vectorclock for clocksi transaction interfaces
catch exception
remove unnecessary logging
synchronous call to interdc vnode
remove waiting and use causal clock in inter dc tests
fix unused variable
remove comments