modules: improve and fix ffac-ssid-changer

[grische]

See

• https://github.com/freifunk-gluon/community-packages/pull/117
• https://github.com/freifunk-gluon/community-packages/pull/116
• https://github.com/freifunk-gluon/community-packages/pull/114

[github-actions[bot]]

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