[nancy][grisou] Disabled mountable on eth4

.../grid5000/sites/nancy/clusters/grisou/nodes/grisou-1.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-10.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-11.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-12.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-13.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-14.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-15.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-16.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-17.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-18.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-19.json

.../grid5000/sites/nancy/clusters/grisou/nodes/grisou-2.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-20.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-21.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-22.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-23.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-24.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-25.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-26.json

...grid5000/sites/nancy/clusters/grisou/nodes/grisou-27.json