postinst: take care of services restarts in HA mode

Needs review!

Addressing https://bugtracker.sipwise.com/view.php?id=1225

From: Michael Prokop <mprokop@sipwise.com>

pkg/kamailio/deb/squeeze/kamailio.postinst

@@ -8,30 +8,51 @@ HOMEDIR=/var/run/kamailio
 
 set -e
 
-# summary of how this script can be called:
-#        * <postinst> `configure' <most-recently-configured-version>
-#        * <old-postinst> `abort-upgrade' <new version>
-#        * <conflictor's-postinst> `abort-remove' `in-favour' <package>
-#          <new-version>
-#        * <deconfigured's-postinst> `abort-deconfigure' `in-favour'
-#          <failed-install-package> <version> `removing'
-#          <conflicting-package> <version>
-# for details, see http://www.debian.org/doc/debian-policy/ or
-# the debian-policy package
-#
-# quoting from the policy:
-#     Any necessary prompting should almost always be confined to the
-#     post-installation script, and should be protected with a conditional
-#     so that unnecessary prompting doesn't happen if a package's
-#     installation fails and the `postinst' is called with `abort-upgrade',
-#     `abort-remove' or `abort-deconfigure'.
+restart_handler() {
+  [ -n "$1" ] || return 1
+
+  if [ -x "/etc/init.d/$1" ]; then
+    if [ -x "$(which invoke-rc.d 2>/dev/null)" ]; then
+      invoke-rc.d "$1" restart || exit $?
+    else
+      /etc/init.d/"$1" restart || exit $?
+    fi
+  fi
+}
+
+initscript_handler() {
+  [ -n "$1" ] || return 1
+
+  if [ -x "/etc/init.d/$1" ]; then
+    update-rc.d "$1" defaults >/dev/null
+    invoke-rc.d "$1" start || exit $?
+  fi
+}
+
+init_handler() {
+  # just invoke init script wrappers on ce systems since
+  # they do not provide ngcp-check_active and we don't
+  # have to handle inactive nodes
+  if ! [ -x "$(which ngcp-check_active 2>/dev/null)" ]; then
+    restart_handler "$1"
+    initscript_handler "$1"
+  else # do not restart daemon on inactive node in pro systems
+    if ngcp-check_active ; then
+      echo "Active node detected, restarting $1"
+      restart_handler "$1"
+    else
+      echo "Inactive node detected, ignoring request to restart $1"
+    fi
+  fi
+}
 
 case "$1" in
     configure)
         adduser --quiet --system --group --disabled-password \
                 --shell /bin/false --gecos "Kamailio" \
                 --home $HOMEDIR kamailio || true
-
+        init_handler kamailio-lb
+        init_handler kamailio-proxy
         ;;
 
     abort-upgrade|abort-remove|abort-deconfigure)