plugins/cni: wait for AWS to drop its CNI configuration file
plugins/cni: wait for AWS to drop its CNI configuration file

The script originally just exited and assumed the kubelet would restart
it, but this is quite disruptive, since that restarts the agent as well.

Additionally, it was discovered that some AWS installations need the
service network to be functioning before the AWS CNI file is written,
leaving clusters in a broken state.

So, change the script to retry looking for the AWS CNI file itself.

Fixes: #21243

Signed-off-by: Casey Callendrello <11fb6d5a105a66c85408b8005c461d53818b736e@isovalent.com>

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