MT#56693 fix parent sound sets list for sound set creation

* in a scenario when a sound set was "edited" and then
  a new one created, in the creation dialog the previously
  edited sound set was missing in the list of available parents

Change-Id: I8d7652a9f7f881be6d700dc4f6cf77dc426261e7

lib/NGCP/Panel/Controller/Sound.pm

@@ -175,6 +175,8 @@ sub base :Chained('sets_list') :PathPart('') :CaptureArgs(1) {
         NGCP::Panel::Utils::Navigation::back_or($c, $c->uri_for('/sound'));
     }
 
+    delete $c->session->{edit_sound_set_id};
+
     my $res = $c->stash->{sets_rs}->find($set_id);
     unless(defined($res)) {
         NGCP::Panel::Utils::Message::error(
@@ -364,6 +366,8 @@ sub delete_sound :Chained('base') :PathPart('delete') {
 sub create :Chained('sets_list') :PathPart('create') :Args() {
     my ($self, $c, $contract_id) = @_;
 
+    delete $c->session->{edit_sound_set_id};
+
     my $posted = ($c->request->method eq 'POST');
     my $form;
     my $params = {};