roachtest: fix logic for exact replication

Previously the check for exact replication was incorrectly counting the
number of replicas that were NOT at the desired replication count. This
fortunately worked becase it was a no-op in the only place that used it
since it was run immediately when all replicas had only a single
replica.

This correctly fixes the check.

Epic: none
Fixes: #109905
Fixes: #109906

Release note: None

pkg/cmd/roachtest/tests/util.go

@@ -105,7 +105,7 @@ func WaitForReplication(
 	var compStr string
 	switch waitForReplicationType {
 	case exactlyReplicationFactor:
-		compStr = "="
+		compStr = "!="
 	case atLeastReplicationFactor:
 		compStr = "<"
 	default: