[master] 4b6ade1de use the right jail level for a system() call

[Nils Goroll]

commit 4b6ade1de5750e1d1c32cc0021adfad57ea9fa35
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Nov 18 15:45:49 2020 +0100

    use the right jail level for a system() call
    
    Ref 31164908ce8e81d116e5a30b7fc404e00f4cc4b3
    
    Fixes #3243

diff --git a/bin/varnishd/mgt/mgt_main.c b/bin/varnishd/mgt/mgt_main.c
index db886f1e6..b848df76c 100644
--- a/bin/varnishd/mgt/mgt_main.c
+++ b/bin/varnishd/mgt/mgt_main.c
@@ -787,7 +787,7 @@ main(int argc, char * const *argv)
 		ARGV_ERR("Cannot create working directory (%s): %s\n",
 		    workdir, vstrerror(errno));
 
-	VJ_master(JAIL_MASTER_FILE);
+	VJ_master(JAIL_MASTER_SYSTEM);
 	AZ(system("rm -rf vmod_cache"));
 	VJ_master(JAIL_MASTER_LOW);