Incorrect content type seen after FORM authentication restores request

Issue

• In some cases, we see Request.getContentType() return an incorrect value (null or another header's value) after FORM authentication completes and restores the original request.
• We see an exception like the followiing in resteasy after FORM authentication

WARN  [org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher] (ajp-localhost%2F127.0.0.1-8009-10) Failed to parse request.
java.lang.IllegalArgumentException: Failure parsing MediaType string: Keep-Alive
        at org.jboss.resteasy.plugins.delegates.MediaTypeHeaderDelegate.parse(MediaTypeHeaderDelegate.java:42)
        at org.jboss.resteasy.plugins.delegates.MediaTypeHeaderDelegate.fromString(MediaTypeHeaderDelegate.java:18)
        at javax.ws.rs.core.MediaType.valueOf(MediaType.java:173)
        at org.jboss.resteasy.plugins.server.servlet.ServletUtil.extractHttpHeaders(ServletUtil.java:90)
        at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:186)
        at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:55)
        at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:50)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)