Use docker tag 5 instead of latest

Change-Id: I1a9a136ed572a69c9867212543280d7055b18dc2
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/docker/mk/Makefile.include b/docker/mk/Makefile.include
index 5f79920..a6df090 100644
--- a/docker/mk/Makefile.include
+++ b/docker/mk/Makefile.include
@@ -4,7 +4,7 @@
 
 all: build
 
-TAG ?= latest
+TAG ?= 5
 
 REPOSITORY_BASE ?= http://osm-download.etsi.org/repository/osm/debian
 RELEASE         ?= ReleaseFOUR-daily