Docker: remove container domain stripping

Stripping the domain is not helpful, as the container that is
provided to us does no longer match the FROM line in the
Dockerfile.

Remove the stripping again and add code to the Download on Demand
service instead.

Build/Docker.pm

@@ -289,10 +289,7 @@ sub parse {
         if ($container ne 'scratch') {
 	  if ($Build::Kiwi::urlmapper && $container =~ /^([^\/]+\.[^\/]+)\/[a-zA-Z0-9]/) {
 	    my $prp = $Build::Kiwi::urlmapper->("registry://$1/");
-	    if ($prp) {
-	      $container =~ s/^[^\/]+\///;	# strip domain
-	      push @containerrepos, $prp;
-	    }
+	    push @containerrepos, $prp if $prp;
 	  }
           $container .= ':latest' unless $container =~ /:[^:\/]+$/;
           $container = "container:$container";