MB-40519 - Rebalance/GetTaskList timeouts with numerous index aliases

Skipping the index aliases while computing the partition count to be
moved during a rebalance operation. This saves a lot of network calls.

Change-Id: I6d875b0183281a8cd39ee6bfa8faba1e0c770ebd
Reviewed-on: http://review.couchbase.org/c/cbgt/+/135956
Well-Formed: Build Bot <build@couchbase.com>
Tested-by: Sreekanth Sivasankaran <sreekanth.sivasankaran@couchbase.com>
Reviewed-by: Abhinav Dangeti <abhinav@couchbase.com>

ctl/ctl.go

@@ -207,6 +207,10 @@ func (ctl *Ctl) getMovingPartitionsCount(keepNodeUUIDs, existingNodes []string)
 	totalPartitions := 0
 	if indexDefs != nil {
 		for _, indexDef := range indexDefs.IndexDefs {
+			// skip any index aliases.
+			if indexDef.SourceType == "nil" {
+				continue
+			}
 			partitions, err := cbgt.CouchbasePartitions(indexDef.SourceType,
 				indexDef.SourceName, indexDef.SourceUUID,
 				indexDef.SourceParams,