fix(NODE-3252): state transistion from DISCONNECTED (#2807)

Author: nbbeeken

lib/core/topologies/replset.js

@@ -558,7 +558,7 @@ var monitorServer = function(host, self, options) {
               self.s.options.secondaryOnlyConnectionAllowed) ||
               self.s.replicaSetState.hasPrimary())
           ) {
-            stateTransition(self, CONNECTED);
+            stateTransition(self, CONNECTING);
 
             // Rexecute any stalled operation
             rexecuteOperations(self);