(copy_aux): Don't use "file delete", since that isn't portable to old

	TCL versions.

src/server/testsuite/lyskomd.0/18.exp

@@ -30,7 +30,7 @@ set myaux "lyskomd.0/aux-items-18.conf"
 proc copy_aux {file} {
     global myaux
 
-    file delete $myaux
+    system "rm -f $myaux"
     file copy $file $myaux
 }