staging/lustre: obd: remove unused data structures

We want to get rid of all uses of time_t, and it turns out
that obd.h contains a bunch of them that are completely unused.

This removes those structures, along with a couple of other
structures and functions in the same file that also turned
out to be unused.

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