Change --show-default-configfiles language to clarify priority

E.g.:
Default list of existing configuration files (5, most important last):
/home/oldeman/lo/easybuild.d/bla.cfg, /home/oldeman/lo/easybuild.d/foo.cfg, /home/oldeman/hi/easybuild.d/bla.cfg, /home/oldeman/hi/easybuild.d/foo.cfg, /home/oldeman/.config/easybuild/config.cfg

easybuild/tools/options.py

@@ -1337,7 +1337,8 @@ def show_default_configfiles(self):
             "* system-level: %s" % os.path.join('${XDG_CONFIG_DIRS:-/etc/xdg}', 'easybuild.d', '*.cfg'),
             "  -> %s => %s" % (system_cfg_glob_paths, ', '.join(flatten(DEFAULT_SYS_CFGFILES)) or "(no matches)"),
             '',
-            "Default list of existing configuration files (%d): %s" % (found_cfgfile_cnt, found_cfgfile_list),
+            "Default list of existing configuration files (%d, most important last):" % found_cfgfile_cnt,
+            found_cfgfile_list,
         ]
         return '\n'.join(lines)
 

test/framework/options.py

@@ -3523,7 +3523,8 @@ def test_show_default_configfiles(self):
         expected_tmpl += '\n'.join([
             "%s",
             '',
-            "Default list of existing configuration files (%d): %s",
+            "Default list of existing configuration files (%d, most important last):",
+            "%s",
         ])
 
         # put dummy cfgfile in place in $HOME (to predict last line of output which only lists *existing* files)