test: disable popen.test

This test is buggy, need to rewrite. Thus to not block other developers
which refer the master branch just disable it.

The test was added in 40a51647 ('test:
unit/popen').

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Alexander Turenko <alexander.turenko@tarantool.org>

test/unit/suite.ini

@@ -3,3 +3,4 @@ core = unittest
 description = unit tests
 release_disabled = fiber_stack.test swim_errinj.test
 is_parallel = True
+disabled = popen.test