Fix IntegrationTestingTutorial network map race condition (#947)

* Ignoring and adding a TODO to a test that fails spuriously during CI.

* Ensure both parties are regsitered with network map in the integration test tutorial and update docs to reflect this best practice.

* Minor readability fix.

docs/source/example-code/src/integration-test/kotlin/net/corda/docs/IntegrationTestingTutorial.kt

@@ -51,6 +51,9 @@ class IntegrationTestingTutorial {
 
             val bobClient = bob.rpcClientToNode()
             val bobProxy = bobClient.start("bobUser", "testPassword2").proxy
+
+            aliceProxy.waitUntilRegisteredWithNetworkMap().getOrThrow()
+            bobProxy.waitUntilRegisteredWithNetworkMap().getOrThrow()
             // END 2
 
             // START 3