DAOS-16458 object: fix invalid DRAM access in obj_bulk_transfer - b26

[Nasf-Fan]

For EC object update via CPD RPC, when calculate the bitmap to skip
some iods for current EC data shard, we may input NULL for "*skips"
parameter. It may cause the old logic in obj_get_iods_offs_by_oid()
to generate some undefined DRAM for "skips" bitmap. Such bitmap may
be over-written by others, as to subsequent obj_bulk_transfer() may
be misguided.

The patch also fixes a bug inside obj_bulk_transfer() that cast any
input RPC as UPDATE/FETCH by force.

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[github-actions]

Ticket title is 'obj_bulk_transfer may read beyond the last element of remote_bulks'
Status is 'In Progress'
Labels: 'scrubbed_2.8'
https://daosio.atlassian.net/browse/DAOS-16458