staging/lustre/ptlrpc: Drop unused client code

These client request/import functions are not used anywhere,
so drop them.

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