utils: evl-trace: fix implicit enable-all command

Signed-off-by: Philippe Gerum <rpm@xenomai.org>

LICENSE

 MIT License
 
-Copyright (c) 2018-2019 Philippe Gerum and the libevl contributors.
+Copyright (c) 2018-2021 Philippe Gerum and the libevl contributors.
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

utils/evl-trace

@@ -91,6 +91,10 @@ fi
 
 for group in $trace_groups
 do
+    if test $group = all; then
+	event_list=""
+	break
+    fi
     if test \! -r $EVL_CMDDIR/trace.$group; then
 	    echo >&2 "no trace group '$group'"
 	    exit 1