Cleanup: ctf: logically dead code

Cleanup: ctf: logically dead code

The `iter_status` variable is guaranteed to be equal to
`BT_MSG_ITER_STATUS_OK` when breaking from the `do-while` loop above.

Coverity report:
  CID 1401337 (#1 of 1): Logically dead code (DEADCODE) dead_error_line:
  Execution cannot reach this statement: goto error;

Reported-by: Coverity (1401337) - Logically dead code
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I51448d800b8ed37e80ce64b77df3905c8042b1bf
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2166
Reviewed-by: Simon Marchi <simon.marchi@efficios.com>
Tested-by: jenkins <jenkins@lttng.org>