importMetadata should handle conflicts between multiple federations

Concerned version

Version: 2.0.14

Summary

/usr/share/lemonldap-ng/bin/importMetadataRenater -m https://pub.federation.renater.fr/metadata/renater/main/main-sps-renater-metadata.xml -r -i "idp-renater-" -s "sp-renater-"
/usr/share/lemonldap-ng/bin/importMetadataRenater -m https://pub.federation.renater.fr/metadata/edugain/main/main-sps-edugain-metadata.xml -r -i "idp-edugain-" -s "sp-edugain-"

Causes some duplicated entityIDs

Possible fixes

When checking if an entityID already exists, check in all declared SP/IDP, not just in the ones that match the prefix