Return success when disabling a disabled record via REST 2

RT's internal API returns "false" when you update a record
to the value it already has. This false return caused a
REST 2 DELETE (which is 'disable' on most records) to return
failure (500) if you disabled an already-disabled queue.

Directly return true if the record is already disabled.

Fixes: I#37591

lib/RT/REST2/Resource/Record/DeletableByDisabling.pm

@@ -57,6 +57,11 @@ with 'RT::REST2::Resource::Record::Deletable';
 
 sub delete_resource {
     my $self = shift;
+
+    # Don't return failure if the resource is already disabled since
+    # the final state is correct, the resource is disabled.
+    return 1 if $self->record->Disabled == 1;
+
     my ($ok, $msg) = $self->record->SetDisabled(1);
     RT->Logger->debug("Failed to disable ", $self->record_class, " #", $self->record->id, ": $msg")
         unless $ok;