rgw: temporarily disable calls to defer_gc() in RGWGetObj

rgw: temporarily disable calls to defer_gc() in RGWGetObj

cls_rgw_gc_queue_update_entry() is known to cause data loss when called
on objects that have not actually been scheduled for garbage collection

RGWGetObj is the only caller, and uses defer_gc() when reads are taking
a long time compared to rgw_gc_obj_min_wait. if an object has since been
deleted and submitted for garbage collection, this allows RGWGetObj to
defer that gc until the entire read completes

by disabling these calls to defer_gc(), very long reads (longer than 1hr,
with default configuration) may fail if the object gets deleted, and a
retry will result in a 404 Not Found error as expected

Fixes: https://tracker.ceph.com/issues/47866
Signed-off-by: Casey Bodley <cbodley@redhat.com>