Use apache for tls-proxy ssl termination

Stud is now abandonware (see https://github.com/bumptech/stud) and is
not packaged in xenial. Lets use Apache for SSL termination since its
there already.

Change-Id: Ifcba410f5969521e8b3d30f02795541c1661f83a
diff --git a/files/debs/tls-proxy b/files/debs/tls-proxy
index dce9c07..5bd8e21 100644
--- a/files/debs/tls-proxy
+++ b/files/debs/tls-proxy
@@ -1 +1 @@
-stud
+apache2