Fix: check illegal combinations of ctrl-url/data-url/ouput/set-url

The lttng CLI must check for illegal combinations of the
--ctrl-url, --data-url, --set-url, and --output options.

The following combinations are mutually exclusive:
  1) --set-url
  2) --ctrl-url + --data-url
  3) --output

Combining these incompatible options resulted in unhelpful
generic error messages since the error is catched a lot farther
than it should.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>