podman --runroot: remove 50 char length restriction

[Luap99]

This was added ages ago in commit c65b359, however in the meantime both podman and conmon can support longer socket paths as they use a workaround to open the path via /proc/self/fd, see openUnixSocket() in libpod/oci_conmon_attach_linux.go

Thus this restriction is not needed anymore and we can drop a workaround in the tests.

Fixes #22272

Does this PR introduce a user-facing change?

The --runroot option now can use paths longer than 50 characters.

[ashley-cui]

LGTM

[flouthoc]

LGTM

[openshift-ci]

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[rhatdan]

/lgtm

[edsantiago]

Thank you for this! Quick followup for posterity: although this seems to fix podman, slirp4netns still can't handle long paths:

# podman [options] run --network slirp4netns:port_handler=slirp4netns -dt -p 18082:8000 quay.io/libpod/alpine:latest /bin/sh
Error: /usr/bin/slirp4netns failed: "sent tapfd=7 for tap0\n
.....
the specified API socket path is too long (>= 108)\n     <<<<<<<<<<
...
Command failed with exit status 126

Not a big deal, since it's slirp, but it does mean we can't use long tmpdir paths in CI tests.

[Luap99]

Thank you for this! Quick followup for posterity: although this seems to fix podman, slirp4netns still can't handle long paths:

# podman [options] run --network slirp4netns:port_handler=slirp4netns -dt -p 18082:8000 quay.io/libpod/alpine:latest /bin/sh
Error: /usr/bin/slirp4netns failed: "sent tapfd=7 for tap0\n
.....
the specified API socket path is too long (>= 108)\n     <<<<<<<<<<
...
Command failed with exit status 126

Not a big deal, since it's slirp, but it does mean we can't use long tmpdir paths in CI tests.

We can report this to slirp4netns, the workaround we use is easy enough to implement there as well. Also it seems to only effect the slirp4netns port_handler (not the default rootlesskit) so it should work fine for most users.