Updated SSH example to ensure it continues working

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)

docs/sources/examples/running_ssh_service.Dockerfile

@@ -2,7 +2,7 @@
 #
 # VERSION               0.0.1
 
-FROM     debian
+FROM    ubuntu:12.04
 MAINTAINER Thatcher R. Peskens "thatcher@dotcloud.com"
 
 # make sure the package repository is up to date

docs/sources/examples/running_ssh_service.md

@@ -12,7 +12,7 @@ quick access to a test container.
     #
     # VERSION               0.0.1
 
-    FROM     debian
+    FROM     ubuntu:12.04
     MAINTAINER Thatcher R. Peskens "thatcher@dotcloud.com"
 
     # make sure the package repository is up to date