Add server test case for the bundle update - query API handler scenario

[ashutosh-narkar]

The query API handler (ie. v1DataPost) should accept client requests even when OPA is performing bundle activation. A recent change updated v1DataPost handler to open a read txn on the store which would prevent api requests from being blocked while a bundle is activating. We should add a server test to exercise this scenario. The test case would open a write transaction on the store and then simulate client requests to ensure that the server still processes them.