sgsn: migrate to the new gprs_ns2_vty configuration

Change the whole vty configuration for NS to be more flexible
and support more setups. Old configurations are invalid.

API change which must be synchronized with libosmocore

For further information see:
https://osmocom.org/projects/libosmocore/wiki/Network_service_(NS)

Depends-on: I8c3f2afecc74b78f7f914f7dce166cbcb63444eb (libosmocore)
Change-Id: Ie9306ab4d4738c2c57a69987086e22771b30657e

TODO-RELEASE

@@ -1,3 +1,4 @@
 #component	what		description / commit summary line
 manual				needs common chapter cs7-config.adoc, vty_cpu_sched.adoc from osmo-gsm-manuals > 0.3.0
 configure.ac	libosmocore	depend on next released libosmocore after 1.4.x with hashtable support
+sgsn		vty/config	change the configuration of the vty config. old configuration are invalid.

doc/examples/osmo-sgsn/osmo-sgsn-accept-all.cfg

@@ -21,9 +21,9 @@ ns
  timer tns-test 30
  timer tns-alive 3
  timer tns-alive-retries 10
- encapsulation udp local-ip 127.0.0.1
- encapsulation udp local-port 23000
- encapsulation framerelay-gre enabled 0
+ bind udp local
+  listen 127.0.0.1 23000
+  accept-ipaccess
 !
 bssgp
 !

doc/examples/osmo-sgsn/osmo-sgsn.cfg

@@ -23,9 +23,9 @@ ns
  timer tns-test 30
  timer tns-alive 3
  timer tns-alive-retries 10
- encapsulation udp local-ip 127.0.0.1
- encapsulation udp local-port 23000
- encapsulation framerelay-gre enabled 0
+ bind udp local
+  listen 127.0.0.1 23000
+  accept-ipaccess
 !
 bssgp
 !

doc/examples/osmo-sgsn/osmo-sgsn_custom-sccp.cfg

@@ -31,9 +31,9 @@ ns
  timer tns-test 30
  timer tns-alive 3
  timer tns-alive-retries 10
- encapsulation udp local-ip 127.0.0.1
- encapsulation udp local-port 23000
- encapsulation framerelay-gre enabled 0
+ bind udp local
+  listen 127.0.0.1 23000
+  accept-ipaccess
 !
 bssgp
 !