issue: #28332
during querycoord's recover, it try to call `DescribeCollection` and
`ShowPartitions` to root coord, to checker whether collection or
partition has been released in rootcoord. but if rootcoord isn't not
ready yet, the rpc will fail, the querycoord panic.
to fix this, we remove rpc call during querycoord's start
Signed-off-by: Wei Liu <wei.liu@zilliz.com>