staging: lustre: clean up format string usages

This fixes up the usage of snprintf, strncpy, and format strings in the
call to kthread_run to avoid ever accidentally allowing a format string
into the thread name.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>