CLI: Address multiple issues.

CLI: Address multiple issues.

* listen uses the variable `s` for the result from ast_poll() then
  overwrites it with the result of accept().  Create a separate variable
  poll_result to avoid confusion since ast_poll does not return a file
  descriptor.
* Resolve fd leak that would occur if setsockopt failed in listen.
* Reserve an extra byte while processing completion results from remote
  daemon.  This fixes a bug where completion processing used strstr() on
  a string that was not '\0' terminated.  This was no risk to the Asterisk
  daemon, the bug was only reachable the remote console process.
* Resolve leak in handle_showchan when the channel is not found.
* Multiple leaks and a deadlock in pbx_config CLI completion.
* Fix leaks in "manager show command".

Change-Id: I8f633ceb1714867ae30ef4e421858f77c14485a9