fix(mongodb): fix cursor instrumentation below 2.0.0

Author: Shadowbeetle

lib/instrumentations/mongodb.js

@@ -54,12 +54,12 @@ function wrapper (mongodb, agent, pkg) {
           continuationMethod = typeof args[args.length - 1] === 'function' ? 'callback' : 'readStream'
         } else {
           // below 2.0.0 if a cursor description is provided, a cursor is returned, otherwise callback is called
-          continuationMethod = queryOptions.cursor ? 'readStream' : 'callback'
+          continuationMethod = queryOptions.cursor ? false : 'callback'
         }
       } else if (typeof args[args.length - 1] === 'function') {
         continuationMethod = 'callback'
       } else if (name === 'find') {
-        continuationMethod = 'readStream'
+        continuationMethod = version && semver.satisfies(version, '>= 2.0.0') ? 'readStream' : false
       } else if (version && semver.satisfies(version, '>= 2.0.0')) {
         continuationMethod = 'promise'
       } else {

lib/instrumentations/mongodb.spec.js

@@ -52,7 +52,7 @@ describe('The mongodb wrapper module', function () {
           method: 'find',
           protocol: 'mongodb',
           url: 'unknown',
-          continuationMethod: 'readStream'
+          continuationMethod: false
         })
     })