box/console: test for exact command before setting eos

When we handle unix console connection we should setup
eos if only we meet "\set output" command in a stream.
For example there could be "\set language" which should
not affect eos settings.

Closes #4568

Reported-by: Alexander Turenko <alexander.turenko@tarantool.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Alexander Turenko <alexander.turenko@tarantool.org>
(cherry picked from commit 092cd675)