[patch] Fix MinIO IPv4 binding and AI Service MinIO secret

[belfortmaycon]

Description

This patch fixes two MinIO-specific issues in the AI Service installation flow.

1. The MinIO deployment template always bound the container listeners to IPv6 ([::]:9090 and [::]:9000), which made the console and API unreachable on IPv4 clusters even when ENABLE_IPV6=false.
2. The AI Service km-s3-secret always populated AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. When INSTALL_MINIO=true, those keys must still exist but be empty; populating them breaks the service for the MinIO-backed configuration.

Impact:

• ENABLE_IPV6=false now renders MinIO listeners on 0.0.0.0:9090 and 0.0.0.0:9000.
• ENABLE_IPV6=true keeps the IPv6 listener values unchanged.
• When INSTALL_MINIO=true, km-s3-secret now renders empty AWS_* values while keeping the S3_* values populated.
• Non-MinIO S3 configurations continue to render the real AWS_* and S3_* credential values.

Test Results

• Static render verification for ibm/mas_devops/roles/minio/templates/minio/minio-deployment.yml.j2 with enable_ipv6=false rendered 0.0.0.0:9090 and 0.0.0.0:9000.
• Static render verification for the same template with enable_ipv6=true rendered [::]:9090 and [::]:9000.
• Static render verification for ibm/mas_devops/roles/aiservice/templates/aiservice/s3-secret.yml.j2 with install_minio=true rendered empty AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY and preserved populated S3_* values.
• Static render verification for the same secret with install_minio=false rendered populated AWS_* and S3_* values.
• Cluster end-to-end validation was not run from this workspace.