migration: update index field when delete or qsort RDMALocalBlock

migration: update index field when delete or qsort RDMALocalBlock

rdma_delete_block function deletes RDMALocalBlock base on index field,
but not update the index field. So when next time invoke rdma_delete_block,
it will not work correctly.

If start and cancel migration repeatedly, some RDMALocalBlock not invoke
ibv_dereg_mr to decrease kernel mm_struct vmpin. When vmpin is large than
max locked memory limitation, ibv_reg_mr will failed, and migration can not
start successfully again.

Signed-off-by: Lidong Chen <lidongchen@tencent.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <1525618499-1560-1-git-send-email-lidongchen@tencent.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Lidong Chen <jemmy858585@gmail.com>