LU-989 ldlm: Fix client's import destruction

LU-989 ldlm: Fix client's import destruction

Move client's import destruction from disconnect to cleanup phase
The patch allows to use connect after disconnect.

Xyratex-bug-id: MRP-288
Signed-off-by: Andriy Skulysh <Andriy_Skulysh@xyratex.com>
Change-Id: I984660a2917a7e4d5c95cd8288dd6974a7c3ccba
Reviewed-by: Alexey Lyashkov <alexey_lyashkov@xyratex.com>
Reviewed-by: Vitaly Fertman <vitaly_fertman@xyratex.com>
Reviewed-on: http://review.whamcloud.com/1963
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Mike Pershin <tappro@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>