there seems to be race conditions related to some tests with sessions
hitting the core and the replicant alternately and rlog.
for intance, if there is some delay in this replication, a new
connection made to the replica with a just-created session in the core
may not have been replicated to the replicant, resulting in a test
failure if it expects the session to be present.
since such replication lags are inherent to the core-replicant
topology, we can try to target only the replicant to avoid seeing this
inconsistent view of the system during the tests.
This parameterizes the Functional Verification Tests (FVTs) that run
in CI to use a replication log (RLOG) role of "replicant" for one of
the nodes. With this addition, our FVTs may explore more scenarios
with data replication.
William Yang