Process hangs with ControlPersist

On OSX 10.10.3, the `easyssh` process hangs after the command has been executed if the user has `ControlPersist yes` in `~/.ssh/config`.

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The issue is about SSH process hangs with ControlPersist on OSX. Look at the easyssh code that handles SSH command execution and process lifecycle. Check how the tool manages SSH connections and child processes. Determine if the hang occurs during connection teardown or signal handling, and see if there are existing tests for SSH behavior.

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