[#943] service/object: Refactor private key fetching during execution

`CommonPrm` structure has private key for remote operations.
It obtained in the beginning of request processing. However,
not every operation triggers remote calls. Therefore, key
might not be used. It is important to avoid early key fetching
because `TokenStore` now returns error if session token does not
exist. This is valid case when container nodes receive request with
session token (for ACL pass) and they should process request locally.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/services/object/get/util.go

@@ -88,12 +88,17 @@ func (c *clientWrapper) getObject(exec *execCtx, info coreclient.NodeInfo) (*obj
 		return exec.prm.forwarder(info, c.client)
 	}
 
+	opts, err := exec.callOptions()
+	if err != nil {
+		return nil, err
+	}
+
 	if exec.headOnly() {
 		return c.client.GetObjectHeader(exec.context(),
 			new(client.ObjectHeaderParams).
 				WithAddress(exec.address()).
 				WithRawFlag(exec.isRaw()),
-			exec.callOptions()...,
+			opts...,
 		)
 	}
 	// we don't specify payload writer because we accumulate
@@ -104,7 +109,7 @@ func (c *clientWrapper) getObject(exec *execCtx, info coreclient.NodeInfo) (*obj
 				WithAddress(exec.address()).
 				WithRange(rng).
 				WithRaw(exec.isRaw()),
-			exec.callOptions()...,
+			opts...,
 		)
 		if err != nil {
 			return nil, err
@@ -115,7 +120,7 @@ func (c *clientWrapper) getObject(exec *execCtx, info coreclient.NodeInfo) (*obj
 
 	return c.client.GetObject(exec.context(),
 		exec.remotePrm(),
-		exec.callOptions()...,
+		opts...,
 	)
 }