Discard non-web traces when searching for a vulnerability not being present (#4871)

Author: CarlesDD

packages/dd-trace/test/appsec/iast/utils.js

@@ -136,6 +136,7 @@ function endResponse (res, appResult) {
 function checkNoVulnerabilityInRequest (vulnerability, config, done, makeRequest) {
   agent
     .use(traces => {
+      if (traces[0][0].type !== 'web') throw new Error('Not a web span')
       // iastJson == undefiend is valid
       const iastJson = traces[0][0].meta['_dd.iast.json'] || ''
       expect(iastJson).to.not.include(`"${vulnerability}"`)