Honor --mods=none with --installed-kernel

It's unlikely that --installed-kernel actually works with --mods=none,
but I think that we should try it and possibly fail to boot rather
than just ignoring the --mods setting.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
diff --git a/virtme/commands/run.py b/virtme/commands/run.py
index db2ce2e..85708ae 100644
--- a/virtme/commands/run.py
+++ b/virtme/commands/run.py
@@ -159,9 +159,13 @@
 
     if args.installed_kernel is not None:
         kver = args.installed_kernel
-        kernel.modfiles = modfinder.find_modules_from_install(
-            virtmods.MODALIASES, kver=kver)
-        kernel.moddir = os.path.join('/lib/modules', kver)
+        if args.mods != 'none':
+            kernel.modfiles = modfinder.find_modules_from_install(
+                virtmods.MODALIASES, kver=kver)
+            kernel.moddir = os.path.join('/lib/modules', kver)
+        else:
+            kernel.modfiles = None
+            kernel.moddir = None
         kernel.kimg = '/usr/lib/modules/%s/vmlinuz' % kver
         if not os.path.exists(kernel.kimg):
             kernel.kimg = '/boot/vmlinuz-%s' % kver