AMBARI-3244. Ambari Client improve errors handling. (Andrew Onischuk via mahadev)

ambari-client/src/test/python/json/error_adding_host.json

@@ -0,0 +1,4 @@
+{
+  "status" : 400,
+  "message" : "Attempted to add unknown hosts to a cluster.  These hosts have not been registered with the server: dev05"
+}