For internal purposes, the rpc_clnt_sigmask() call is replaced by
 a call to rpc_task_sigmask(), which ensures that the current task
 sigmask respects both the client cl_intr flag and the per-task NOINTR flag.

 Problem noted by Jiaying Zhang.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>