Add replication test with multiple channels

[raghusarangapani]

Test case as reported by a customer:

• Have 3 channels.
• One shot replication - continuous set to false.
• Start three independent replications one after another - start the first replicator to pull the docs from the channel. once the replicator is stopped, create the second replicator for the second channel and then the third.
• Verify that all the docs from the corresponding channels get replicated.

Assigning it to @sridevi-15 as she has been working on the replication tests.