network: actually show the unexpected flags

network: actually show the unexpected flags

The original version would yield a slightly _unexpected_ message for
this [Address] section:

[Address]
Address=10.9.3.1/24
HomeAddress=yes
ManageTemporaryAddress=yes

systemd-networkd[68396]: /run/systemd/network/25-address-static.network: unexpected address flags "n/a" were configured. Ignoring [Address] section from line 144.

Let's instead show the unexpected flags:

systemd-networkd[69160]: /run/systemd/network/25-address-static.network: unexpected address flags "home-address,manage-temporary-address" were configured. Ignoring [Address] section from line 144.