TT#142402 Fix v1 'Back' button navigation on v2 (iframe inside iframe)

The ngcp-panel v1 codebase uses 'back=' GET parameters to record
all the navigation path and store it into the session array:
'$c->session->{redirect_targets}'.

On switch from v1 to v2 using the link 'GO TO NEW ADMIN PANEL',
the function 'login_to_v2' is not using the concept of 'back=' GET param,
but ngcp-panel still receives and stores the last value with 'empty' path:

> $VAR1 = bless( do{\(my $o = 'https://x.x.x.x:1443/')}, 'URI::https' );
> $VAR2 = bless( do{\(my $o = 'https://x.x.x.x:1443/subscriber/155/details')}, 'URI::https' );
> $VAR3 = bless( do{\(my $o = 'https://x.x.x.x:1443/subscriber')}, 'URI::https' );
> $VAR4 = bless( do{\(my $o = 'https://x.x.x.x:1443/dashboard')}, 'URI::https' );

The navigation above is a recorded browsing path on v1 (in a reverse order):
 - login to ngcp-panel (dashboard page is opened),
 - open 'Subscribers'
 - open details for some subscriber with id 155
 - open subscriber preferences
 - click on link 'GO TO NEW ADMIN PANEL'.
As a result user is still located on the same page "Preferences",
but not on v1 but v2 interface. The empty value is inserted into
the array '$c->session->{redirect_targets}' (which is wrong).

The empty path 'https://x.x.x.x:1443/' brakes v2 navigation
for v1 'Back' button inside iframe.

It causes loading of iframe inside iframe,
which happens on v2 due to list of redirections:
 - clicking on v1 button 'back' inside v2 iframe requests https://x.x.x.x:1443/back
 - it triggers navigation to the top element array 'https://x.x.x.x:1443/' which is wrong/corrupted.
 - loading '/' cause 302 redirect to '/v2/' (as 'v2' is a default UI for mr10.0+)
 - loading '/v2/' inside iframe cause the issue with 'v2' content inside 'v2' iframe.

This is a commit to prevent inserting an empty 'back_uri' into
the session array '$c->session->{redirect_targets}'.

Change-Id: I69df4320fa8cde4d23a7d9dd18ffb5eb06ee8df1

lib/NGCP/Panel/Utils/Navigation.pm

@@ -20,7 +20,7 @@ sub check_redirect_chain {
         $back_uri->query_param_delete('back');
         delete $c->request->params->{back};
         if(@{ $c->session->{redirect_targets} }) {
-            unless(${ $c->session->{redirect_targets} }[0]->path eq $back_uri->path) {
+            unless((${ $c->session->{redirect_targets} }[0]->path eq $back_uri->path) || ($back_uri->path eq '/') ) {
                 unshift @{ $c->session->{redirect_targets} }, $back_uri
             }
                 # in case you press F5 with a back-uri in the url