public Descriptor addServlet(int port, String path, HttpServlet servlet) {
    Descriptor descriptor = new Descriptor(port, path, servlet);
    return addServlet(descriptor);
  }
Adds a servlet instance.
<p>The servlet port can be shared between servlets; if 0, the system will provide
a port. If the port is &lt; 0, the system will provide a port dedicated (ie non-shared)
to the servlet.</p>

@param port    the servlet port
@param path    the servlet path
@param servlet a servlet instance
@return a descriptor
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ServletServerBuilder.java