workaround "root" field name bug

2.0 master has a bug that makes a field named "root" not allowed anymore.
This commit is a workaround in order for these graphs to be displayed again.

Proper resolution is due in master, not in the plugins. But patch is much more
invasive. So delaying it to 2.1.

plugins/lib/Munin/Plugin.pm

@@ -167,6 +167,9 @@ sub clean_fieldname ($) {
     # Replace remaining illegals with _
     $name =~ s/[^A-Za-z0-9_]/_/g;
 
+    # "root" is *not* allowed due to a 2.0 bug
+    $name = "__root" if $name eq "root";
+
     return $name;
 }
 

plugins/plugin.sh.in

@@ -9,8 +9,9 @@ clean_fieldname () {
     # very much still break munin.
     #
     # usage: name="$(clean_fieldname "$item")"
-    # 
-    echo "$@" | sed -e 's/^[^A-Za-z_]/_/' -e 's/[^A-Za-z0-9_]/_/g'
+
+    # "root" is *not* allowed due to a 2.0 bug
+    echo "$@" | sed -e 's/^[^A-Za-z_]/_/' -e 's/[^A-Za-z0-9_]/_/g' -e 's/^root$/__root/'
 }