issue: #36970
cause release segment and balance channel may happen at same time, and
before new delegator become serviceable, if release segment exeuctes on
new delegator, and search/query comes on old delegator, then release
segment and query segment happens in parallel, if release segment
execute first in worker, then search/query will got a SegmentNodeLoaded
error.
This PR add serviceable filter on delegator, then all load/release
segment operation will happens on serviceable delegator.
Signed-off-by: Wei Liu <wei.liu@zilliz.com>