[#1403] engine: Iterate all shards while seaching for an object

Before, when searching for an object, we iterated over shards and stopped
right after we found the object. Currently, we need to itarate over all
shards, because, when the object and its GC mark are stored separately, we
could find the object earlier than its GC mark.

Signed-off-by: Aleksey Savchuk <a.savchuk@yadro.com>

pkg/local_object_storage/engine/get.go

@@ -94,6 +94,10 @@ func (e *StorageEngine) get(ctx context.Context, prm GetPrm) (GetRes, error) {
 		return GetRes{}, errNotFound
 	}
 
+	if client.IsErrObjectAlreadyRemoved(it.OutError) {
+		return GetRes{}, it.OutError
+	}
+
 	if it.Object == nil {
 		if !it.HasDegraded && it.ShardWithMeta.Shard == nil || !client.IsErrObjectNotFound(it.OutError) {
 			return GetRes{}, it.OutError
@@ -146,7 +150,10 @@ func (i *getShardIterator) tryGetWithMeta(ctx context.Context) {
 		res, err := sh.Get(ctx, i.ShardPrm)
 		if err == nil {
 			i.Object = res.Object()
-			return true
+			// Keep iterating over shards because the object's GC mark can be
+			// stored on another shard. For more information, please refer to
+			// https://git.frostfs.info/TrueCloudLab/frostfs-node/pulls/1403.
+			return false
 		}
 
 		if res.HasMeta() {