S3CSI-223: Upgrade mount-s3 from v1.18.0 to v1.21.0

[anurag4DSB]

Summary

• Upgrade Mountpoint for S3 (mount-s3) from v1.18.0 to v1.21.0
• Picks up critical fixes: close-reopen race, panic-on-unlink, unified memory pool
• Also adds: concurrent directory listing, NO_PROXY support

Changes

• Dockerfile: Change ARG MOUNTPOINT_VERSION=1.18.0 to ARG MOUNTPOINT_VERSION=1.21.0

Key mount-s3 Improvements (v1.18.0 → v1.21.0)

• v1.19.0: Unified memory pool, NO_PROXY env support
• v1.20.0: Concurrent directory listing, close-reopen race fix
• v1.21.0: Panic-on-unlink fix, performance improvements

Test Plan

• Dockerfile edit verified against upstream
• CI E2E: Full E2E suite runs against the built container image, validating new mount-s3 binary: data persistence, file/directory permissions, cache, multi-volume, credentials, dynamic provisioning, and performance.

Issue: S3CSI-223

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
128	1	127	58

View the top 1 failed test(s) by shortest run time

Scality CSI Driver for S3 E2E Suite::[It] [sig-storage] CSI Volumes [Driver: s3.csi.scality.com] [Testpattern: Pre-provisioned PV (default fs)] filepermissions should handle mv correctly (metadata intact or ENOTSUP) [sig-storage]

Stack Traces | 18.5s run time

[FAILED] Expected an error to have occurred.  Got:
    <nil>: nil
In [It] at: .../e2e/customsuites/filepermissions.go:1153 @ 02/16/26 07:14:47.252

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