fix ssh_wrap to use Shellwords.escape - #996

What does this PR do?

ssh_wrap passed the command, its arguments, and env values through to ssh unescaped.
SSH does no escaping of its own — the remote shell re-parses the whole command string — so
any argument containing a shell metacharacter gets mangled.

The reporter's example: an LSF resource request like -R select[mem>4000] has its >
interpreted as a redirect on the remote host, so the job is never submitted correctly.
Arguments with spaces split, and env values were interpolated raw into
export KEY=VALUE;.

ssh_wrap now shell-escapes cmd_args and env values. The escaping happens after the
existing early return:

return cmd, cmd_args if submit_host.to_s.empty?

so sites not using submit_host are unaffected — they return before reaching it, and
Open3.capture3 passes arguments as separate argv entries with no shell involved.

Related issue

Closes #923

Testing

• Tests included
• No tests needed — reason: ___

Three existing assertions in spec/job/adapters/helper_spec.rb updated — they used a
Job Name fixture with a space and asserted the unescaped output. The two local-path
assertions are unchanged and confirm no behavior change without submit_host.

New test/job/adapters/helper_test.rb covers the reporter's select[mem>4000] case, a
semicolon, env values with spaces, and the no-submit_host path.

bundle exec rake test and bundle exec rake spec are green.

Checklist

• Follows project code style and conventions
• Documentation provided (if new feature, adapter or behavior change) — N/A
• This is a large feature and was discussed in an issue first (if applicable) — N/A

Anything else?

Sites currently working around this will need to stop. @keysmashes noted manually
.shellescape-ing native arguments in submit.yml.erb to get LSF submission working
over SSH. After this, those get escaped twice. Worth a release note.

On double-escaping, per @johrstrom's caution on the issue: I checked the other escaping
in the adapters. torque.rb:136 escapes envvars, but that is in the hash-native branch
which submits through the pbs-ruby bindings, not through ssh_wrap — separate path, no
overlap. The Shellwords use in kubernetes/helper.rb is a split, not an escape.

Affects every adapter that submits over SSH: slurm, psij, pbspro, sge, htcondor, torque,
lsf.