[environments] Used available_on method to update environments present on sites.

...d5000/sites/bordeaux/environments/lenny-x64-base-2.1.json

...d5000/sites/bordeaux/environments/lenny-x64-base-2.2.json

...id5000/sites/bordeaux/environments/lenny-x64-big-2.1.json

...id5000/sites/bordeaux/environments/lenny-x64-big-2.2.json

...id5000/sites/bordeaux/environments/lenny-x64-nfs-2.1.json

...id5000/sites/bordeaux/environments/lenny-x64-nfs-2.2.json

...d5000/sites/grenoble/environments/lenny-x64-base-2.1.json

...id5000/sites/grenoble/environments/lenny-x64-big-2.1.json

...id5000/sites/grenoble/environments/lenny-x64-big-2.2.json

...id5000/sites/grenoble/environments/lenny-x64-nfs-2.1.json

...id5000/sites/grenoble/environments/lenny-x64-nfs-2.2.json

...id5000/sites/grenoble/environments/lenny-x64-xen-1.0.json

...grid5000/sites/lille/environments/lenny-x64-base-2.1.json

...grid5000/sites/lille/environments/lenny-x64-base-2.2.json

.../grid5000/sites/lille/environments/lenny-x64-big-2.1.json

.../grid5000/sites/lille/environments/lenny-x64-big-2.2.json

.../grid5000/sites/lille/environments/lenny-x64-nfs-2.1.json

.../grid5000/sites/lille/environments/lenny-x64-nfs-2.2.json

.../grid5000/sites/lyon/environments/lenny-x64-base-2.1.json

.../grid5000/sites/lyon/environments/lenny-x64-base-2.2.json