Flaky TestPluginSocketBackwardsCompatible/detached/the_main_CLI_exits_after_3_signals

Description

https://github.com/docker/cli/actions/runs/13927834382/job/38976974170?pr=5918#step:5:765

 === FAIL: e2e/cli-plugins TestPluginSocketBackwardsCompatible/detached/the_main_CLI_exits_after_3_signals (1.12s)
    socket_test.go:111: docker --config /tmp/plugin-test-2773236125 presocket test-no-socket
    socket_test.go:139: assertion failed: 255 (int) != 1 (int)
    socket_test.go:144: assertion failed: 
        --- ←
        +++ →
        @@ -1 +1,2 @@
        +got 3 SIGTERM/SIGINTs, forcefully exiting

Reproduce

CI runs

Expected behavior

No response

docker version

Client: Docker Engine - Community
   Version:           26.1.3
   API version:       1.45
   Go version:        go1.21.10
   Git commit:        b72abbb
   Built:             Thu May 16 08:33:35 2024
   OS/Arch:           linux/amd64
   Context:           default
  
  Server: Docker Engine - Community
   Engine:
    Version:          26.1.3
    API version:      1.45 (minimum version 1.24)
    Go version:       go1.21.10
    Git commit:       8e96db1
    Built:            Thu May 16 08:33:35 2024
    OS/Arch:          linux/amd64
    Experimental:     true
   containerd:
    Version:          1.7.25
    GitCommit:        bcc810d6b9066471b0b6fa75f557a15a1cbf31bb
   runc:
    Version:          1.2.4
    GitCommit:        v1.2.4-0-g6c52b3f
   docker-init:
    Version:          0.19.0
    GitCommit:        de40ad0

docker info

Client: Docker Engine - Community
   Version:    26.1.3
   Context:    default
   Debug Mode: false
   Plugins:
    buildx: Docker Buildx (Docker Inc.)
      Version:  v0.21.2
      Path:     /usr/libexec/docker/cli-plugins/docker-buildx
    compose: Docker Compose (Docker Inc.)
      Version:  v2.27.1
      Path:     /usr/libexec/docker/cli-plugins/docker-compose
  
  Server:
   Containers: 0
    Running: 0
    Paused: 0
    Stopped: 0
   Images: 0
   Server Version: 26.1.3
   Storage Driver: overlay2
    Backing Filesystem: extfs
    Supports d_type: true
    Using metacopy: false
    Native Overlay Diff: false
    userxattr: false
   Logging Driver: json-file
   Cgroup Driver: systemd
   Cgroup Version: 2
   Plugins:
    Volume: local
    Network: bridge host ipvlan macvlan null overlay
    Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
   Swarm: inactive
   Runtimes: io.containerd.runc.v2 runc
   Default Runtime: runc
   Init Binary: docker-init
   containerd version: bcc810d6b9066471b0b6fa75f557a15a1cbf31bb
   runc version: v1.2.4-0-g6c52b3f
   init version: de40ad0
   Security Options:
    apparmor
    seccomp
     Profile: builtin
    cgroupns
   Kernel Version: 6.8.0-1021-azure
   Operating System: Ubuntu 24.04.2 LTS
   OSType: linux
   Architecture: x86_64
   CPUs: 4
   Total Memory: 15.62GiB
   Name: fv-az1676-322
   ID: 037eeb9a-fa35-4bec-af2b-1b30adfbcf1e
   Docker Root Dir: /var/lib/docker
   Debug Mode: false
   Username: githubactions
   Experimental: true
   Insecure Registries:
    127.0.0.0/8
   Live Restore Enabled: false

Additional Info

No response

Start with e2e/cli-plugins and inspect socket_test.go around lines 111-144, then run TestPluginSocketBackwardsCompatible/detached/the_main_CLI_exits_after_3_signals as in CI. Determine why the assertion intermittently receives the forceful-exit message; done means the test reliably passes without the unexpected output or exit status.