Ensure XDCR works on new added node - preflight test

A number of cases in support involving XDCR end up being because of a connective issue (DNS lookup and Firewalls). With a clustered system it is tricky for the user to test that each node in the source cluster can contact all the nodes in the target cluster. For example with a 15 node source cluster and a 5 node target cluster that would be a total of 75 tests.

It would be much better for support and the user if Couchbase Server had a test XDCR connective button in the UI. Where every node in the target cluster would do the following and display the results with a clear message!

• DNS lookup of the reference IP address
• Get the target cluster map
• DNS lookup of each node in the target
• Create a connection to each port on each node that is used.

Maybe extra tests when encryption is used.