Fix tags not being applied on AWS EBS Snapshots

[ruimarinho]

This PR resolves an issue where tags specified via command-line arguments were not being correctly applied to snapshots.

Consider the following example:

/usr/bin/barman-cloud-backup --cloud-provider aws-s3 \
--aws-region us-east-1 \
--tags environment,production project,my-project service,barman \
--snapshot-disk $VOLUME_ID \
--snapshot-instance $INSTANCE_ID \
s3://test/barman postgres

Previously, the tags environment, project and service were not included in the snapshot tags; only a single tag (Name) was set by default. This omission made it difficult to filter snapshots based on tags, which is crucial for maintaining security and managing resources effectively.

[diogotorres97]

Tested alongside #1005 and is working as expected!

[diogotorres97]

ping