Fix Docker image tag conflict in redis_combined_features target

[Copilot]

Problem

CI failed when running combined Redis tests: both AOF and RDB tests attempted to build images with identical tags (redis:test_net_13) but different IMAGE_TYPE build args, causing Docker to reject the second build.

ERROR: image "docker.io/library/redis:test_net_13": already exists

Changes

Makefile: Modified redis_combined_features target to use --tf.stop=true for the first (AOF) test instead of --tf.stop=false.

• First test now removes containers/images after completion (--tf.stop=true) while preserving staging directory (--tf.clean=false)
• Second test recreates network and builds fresh images with different IMAGE_TYPE
• Staging directory reuse still provides time savings (avoids re-copying wal-g source, Go deps already installed)

# Before: --tf.stop=false caused image tag conflict
cd tests_func/ && REDIS_VERSION=$(REDIS_VERSION) IMAGE_TYPE=aof ... --tf.stop=false ...

# After: --tf.stop=true removes images, allows rebuild with new IMAGE_TYPE
cd tests_func/ && REDIS_VERSION=$(REDIS_VERSION) IMAGE_TYPE=aof ... --tf.stop=true ...

Original prompt

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This section details on the original issue you should resolve

<issue_title>[FEATURE] combine aof and rdb test together</issue_title>
<issue_description>### What feature would you like?

prepation for redis testing takes time, I want both aof and rdb tests to run one after another in the same run

Why is this feature useful?

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [FEATURE] combine aof and rdb test together #42

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