MXS-2854: Repeat read on schema event

The read needs to be repeated if MaxScale sends a schema event.

connectors/cdc-connector/cdc_connector.cpp

@@ -449,16 +449,28 @@ SRow Connection::read()
     SRow rval;
     std::string row;
 
+    while (true)
+    {
         if (read_row(row))
         {
             json_error_t err;
             json_t* js = json_loads(row.c_str(), JSON_ALLOW_NUL, &err);
 
             if (js)
+            {
+                if (is_schema(js))
+                {
+                    m_schema = row;
+                    process_schema(js);
+                    json_decref(js);
+                    continue;
+                }
+                else
                 {
                     rval = process_row(js);
                     json_decref(js);
                 }
+            }
             else
             {
                 m_error = "Failed to parse JSON: ";
@@ -466,6 +478,9 @@ SRow Connection::read()
             }
         }
 
+        break;
+    }
+
     return rval;
 }