The ibv_cmd_* create functions need to set context

The ibv_cmd_* create functions need to set context

If the ibv_cmd_* create function succeeds, then the object context
pointer must be set by that function so that the corresponding destroy
function will work.  This avoids problems in the error cleanup path of
a low-level driver's create function that fails after calling an
ibv_cmd_* create function.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>