Fix path for plugin server demo

Change-Id: I571315051009b3ee9e333f2075be298c62752e46
diff --git a/t/server/plugin.pl b/t/server/plugin.pl
index 974a33f..97df0e8 100644
--- a/t/server/plugin.pl
+++ b/t/server/plugin.pl
@@ -1,6 +1,6 @@
 use Mojolicious::Lite;
 
-my $base = app->home->child('..');
+my $base = app->home->child('..', '..');
 
 push @{app->static->paths}, $base->child('dev');