api: annotate download endpoints

both the task and system log API endpoints support downloading the log data.

annotate the API method schema accordingly to allow passing the newly
introduced checks in the API handler that limit download functionality to
annotated endpoints.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

PVE/API2/Nodes.pm

@@ -815,6 +815,7 @@ __PACKAGE__->register_method({
 	check => ['perm', '/nodes/{node}', [ 'Sys.Syslog' ]],
     },
     protected => 1,
+    download => 1,
     parameters => {
 	additionalProperties => 0,
 	properties => {

PVE/API2/Tasks.pm

@@ -327,6 +327,7 @@ __PACKAGE__->register_method({
 	user => 'all',
     },
     protected => 1,
+    download => 1,
     description => "Read task log.",
     proxyto => 'node',
     parameters => {