nova: don't unzip images with grub

Causes trouble if a gz image is loaded via grub and later used as initrd for a
Linux VM (e.g. with Seoul VMM)

Discovered during Turmvilla scenario genodelabs#1552 and issue genodelabs#1733.

tool/run/boot_dir/nova

@@ -64,7 +64,7 @@ proc run_boot_dir {binaries} {
 		puts $fh " module /genode/config"
 		foreach binary $binaries {
 			if {$binary != "core"} {
-				puts $fh " module /genode/$binary" } }
+				puts $fh " modulenounzip /genode/$binary" } }
 		close $fh
 	}