Add generic thisproperty() in xymon script, analagous to thisquota()

ROOT/usr/lib/xymon/client/ext/zfs-backups

@@ -230,13 +230,19 @@ sub space($) {
 
 }
 
-sub thisquota($) {
+sub thisproperty($$) {
     my $zfs=shift;
-    my $quota=`sudo zfs get quota -Hp -ovalue $zfs`;
+    my $property=shift;
+    my $quota=`sudo zfs get $property -Hp -ovalue $zfs`;
     chomp $quota;
     return $quota;
 }
 
+sub thisquota($) {
+    my $zfs=shift;
+    return thisproperty($zfs, 'quota');
+}
+
 sub parentquota($) {
     my $zfs = shift;
     my $parent = join('/', (split('/', $zfs))[0..1]);