MRP-1611 obd: eliminate extra call to cfs_waitq_signal

call to cfs_waitq_signal() in do_writepages_interpret() is wrong.
obd_info's update callback (lov_update_set) waked up the waiter
already and it might already free the wait queue.

remove call to cfs_waitq_signal() from do_writepages_interpret()
eliminate extra argument of o_writepages method in obd_ops

Signed-off-by: Vladimir Saveliev <vladimir_saveliev@xyratex.com>
Change-Id: I9f1d0b853f73c406495d986f09f13d32f2f42ffc
Reviewed-on: http://morpheus.xyus.xyratex.com:8443/gerrit/1333
Tested-by: Jenkins
Reviewed-by: Andrew Perepechko <Andrew_Perepechko@xyratex.com>
Tested-by: Elena Gryaznova <Elena_Gryaznova@xyratex.com>
Reviewed-by: Alexey Lyashkov <Alexey_Lyashkov@xyratex.com>
Reviewed-by: Denis Kondratenko <Denis_Kondratenko@xyratex.com>