Improve behaviour of admin module in containers

[alexandrecuer]

1. The admin module is very verbose as it complains with iostat and systemctl
   
2. It is not possible to upgrade the modules which have been modified from the admin module UI
   
   emoncms cannot be upgraded but this is becuase in the container, the emoncms doc has been deleted, but the doc should be in a distinct repo
   for the core, ti is not really a pb as normally you change the container version when you want to test a new version of emoncms
   for the modules, you should have the ability to change version or to test the master

corrected :

• postprocess : adapt model and shell script so they also work in container emoncms/postprocess#32
• admin : Adapt admin model for a correct behaviour in container emoncms/emoncms#1917

to do :

• sync : adapt shell script so it also works in container emoncms/sync#40
• backup : adapt shell scripts to work in container emoncms/backup#83
• admin bug correction : Readjust admin model to work with BOTH standalone & original containers emoncms/emoncms#1918