staging/lustre/ptlrpc: Remove server-specific health checks

ptlrpc_service_health_check is only used on a service, so
it makes no point to retain it in the client code.
Also removing it's helpers: ptlrpc_svcpt_health_check and
ptlrpc_nrs_req_peek_nolock

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>