[all] yamllint compliance

.gitlab-ci.yml

input/grid5000/disks.yaml

input/grid5000/grid5000.yaml

input/grid5000/ipv6.yaml

input/grid5000/sites/grenoble/clusters/dahu/dahu.yaml

...t/grid5000/sites/grenoble/clusters/dahu/dahu_metrics.yaml

input/grid5000/sites/grenoble/clusters/troll/troll.yaml

...grid5000/sites/grenoble/clusters/troll/troll_metrics.yaml

input/grid5000/sites/grenoble/clusters/troll/troll_pdu.yaml

...t/grid5000/sites/grenoble/clusters/yeti/yeti_metrics.yaml

input/grid5000/sites/grenoble/grenoble.yaml

input/grid5000/sites/grenoble/networks/gw.yaml

input/grid5000/sites/grenoble/pdus.yaml

input/grid5000/sites/grenoble/servers/servers.yaml

input/grid5000/sites/grenoble/servers/virtual.yaml

input/grid5000/sites/lille/clusters/chetemi/chetemi.yaml

...rid5000/sites/lille/clusters/chetemi/chetemi_metrics.yaml

input/grid5000/sites/lille/clusters/chiclet/chiclet.yaml

...rid5000/sites/lille/clusters/chiclet/chiclet_metrics.yaml

input/grid5000/sites/lille/clusters/chifflet/chifflet.yaml