Merge pull request #2798 from freifunk-gluon/backport-2792-to-v2022.1.x

[Backport v2022.1.x] gluon-core:  sleep to wait for device initialisations

package/gluon-core/files/etc/uci-defaults/zzz-gluon-upgrade

 #!/bin/sh
 
+# Work around an issue with wifi setup timing by waiting a bit
+# while device initialisation is ongoing.
+# https://github.com/freifunk-gluon/gluon/issues/2779
+sleep 3
+
 gluon-reconfigure
 
 exit 0