Test: after starting server, send SIGHUP to server process and run ls on mountpoint.

Server process is hung executing an infinite loop in rpcsvc_program_actor. Traversal of List storing registering programs is resulting in an infinite loop.

Cause: list_add_tail is done on same list_head object more than once. This happens since we are adding global program structures into svc registered program list and when SIGHUP is sent the graph is reinitialized and rpcsvc_program_register is called for second time on a program object that is already in list of registered programs.