TT#29456 Add netscript Dockerfile for stretch

Change-Id: Ie2bbe79607c694a9749ee3ebf2dd96422ea3fc63

t/Dockerfile

@@ -1,5 +1,5 @@
-# DOCKER_NAME=netscript-jessie
-FROM docker.mgm.sipwise.com/sipwise-jessie:latest
+# DOCKER_NAME=netscript-stretch
+FROM docker.mgm.sipwise.com/sipwise-stretch:latest
 
 # Important! Update this no-op ENV variable when this Dockerfile
 # is updated with the current date. It will force refresh of all
@@ -19,13 +19,13 @@ WORKDIR /code/
 # When you want to build the base image from scratch
 # jump to the next section if you don't want to build yourself!:
 #
-# % docker build --tag="lua-ngcp-kamailio-jessie" -f t/Dockerfile .
-# % docker run --rm -i -t -v $(pwd):/code:rw lua-ngcp-kamailio-jessie:latest bash
+# % docker build --tag="lua-ngcp-kamailio-stretch" -f t/Dockerfile .
+# % docker run --rm -i -t -v $(pwd):/code:rw lua-ngcp-kamailio-stretch:latest bash
 #
 # Use the existing docker image:
-# % docker pull docker.mgm.sipwise.com/lua-ngcp-kamailio-jessie
+# % docker pull docker.mgm.sipwise.com/lua-ngcp-kamailio-stretch
 # NOTE: run the following command from root folder of git repository:
-# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/lua-ngcp-kamailio-jessie:latest bash
+# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/lua-ngcp-kamailio-stretch:latest bash
 #
 # Inside docker (the command is in history, just press UP button):
 #   ./t/testrunner