Add missing JSP support for Jetty in tests

Some tests using an embedded Jetty server through the JettyFeature need JSP support, for example if an authentication attempt fails and gets redirected to the login.jsp page.
Since NXP-10821, the following dependencies are not included any more, and have therefore been added explicitly to the nuxeo-runtime-test pom:

<dependency>
  <groupId>org.mortbay.jetty</groupId>
  <artifactId>jsp-api-2.1</artifactId>
</dependency>
<dependency>
  <groupId>org.mortbay.jetty</groupId>
  <artifactId>jsp-2.1</artifactId>
</dependency>