TT#56007 TT#55864 make RTPENGINE rules UDP only

The rtpengine kernel module only cares about UDP packets, so narrow down
our iptables rule accordingly.

Change-Id: I33856efa6b39372104b05ec0dc6f34ad0b5e0cbd
(cherry picked from commit cd23c05044)

debian/ngcp-rtpengine-iptables-setup

@@ -52,12 +52,14 @@ firewall_setup()
 
   iptables -N rtpengine 2>/dev/null
   iptables -D INPUT -j rtpengine 2>/dev/null
-  iptables -I INPUT -j rtpengine
+  iptables -D INPUT -p udp -j rtpengine 2>/dev/null
+  iptables -I INPUT -p udp -j rtpengine
   iptables -D rtpengine -p udp -j RTPENGINE --id "$TABLE" 2>/dev/null
   iptables -I rtpengine -p udp -j RTPENGINE --id "$TABLE"
   ip6tables -N rtpengine 2>/dev/null
   ip6tables -D INPUT -j rtpengine 2>/dev/null
-  ip6tables -I INPUT -j rtpengine
+  ip6tables -D INPUT -p udp -j rtpengine 2>/dev/null
+  ip6tables -I INPUT -p udp -j rtpengine
   ip6tables -D rtpengine -p udp -j RTPENGINE --id "$TABLE" 2>/dev/null
   ip6tables -I rtpengine -p udp -j RTPENGINE --id "$TABLE"
 }