move the service enable statement

[keomabrun]

This fixes https://github.com/labriqueinternet/hotspot_ynh/issues/47

[alexAubin]

Merging because app is broken in the meantime :

• https://forum.yunohost.org/t/installation-de-hotspot-wifi-plante/7125
• https://ci-apps.yunohost.org/ci/job/1975