Context cancellation that aborts a non-essential Redis operation must
not be logged as an error because the operation is intentionally
canceled.
We are actually considering them not to be an error in following
operation because of the same reason and we return a RPC canceled status
code.
On the other hand it doesn't make sense to continue if the context is
canceled because although this is a non-essential operation if this one
is canceled due to the context the next one will be canceled for the
same reason, hence, we return earlier.
Change-Id: Ib3331975adeb06367d1ea0a578263ef50ae3f079
aa1f50197a