This changes only the handlers which deals with idr based objects to
use the new idr allocation, fetching and destruction schema.
This patch consists of the following changes:
(1) Allocation, fetching and destruction is done via idr ops.
(2) Context initializing and release is done through
    uverbs_initialize_ucontext and uverbs_cleanup_ucontext.
(3) Ditching the live flag. Mostly, this is pretty straight
    forward. The only place that is a bit trickier is in
    ib_uverbs_open_qp. Commit [1] added code to check whether
    the uobject is already live and initialized. This mostly
    happens because of a race between open_qp and events.
    We delayed assigning the uobject's pointer in order to
    eliminate this race without using the live variable.

[1] commit a040f95d
	("IB/core: Fix XRC race condition in ib_uverbs_open_qp")
Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>