move more cassandra-specific logic out of outbound

Author: Jordi Bertran de Balanda

packages/datadog-plugin-cassandra-driver/src/index.js

@@ -10,8 +10,8 @@ class CassandraDriverPlugin extends DatabasePlugin {
   constructor (...args) {
     super(...args)
 
-    this.addTraceSub('connect', message => {
-      this.connect(message)
+    this.addTraceSub('connect', url => {
+      this.addHost(url.hostname, url.port)
     })
   }
 

packages/dd-trace/src/plugins/outbound.js

@@ -5,10 +5,6 @@ const TracingPlugin = require('./tracing')
 
 // TODO: Exit span on finish when AsyncResource instances are removed.
 class OutboundPlugin extends TracingPlugin {
-  connect (url) {
-    this.addHost(url.hostname, url.port)
-  }
-
   addHost (hostname, port) {
     const span = this.activeSpan