This ought to make it so that all single statements (Exec- or Query-) on
a CockroachDB backend will get retried as necessary. As there is no need
for savepoints to be allocated or released in this case, there is no
round-trip overhead except when statements actually do need to be
retried.
Change-Id: Ibd7f1725ff727477c456cb309120d080f3cd7099
