POSIX poll should always return POLLERR and POLLHUP in revents, regardless
of whether they were requested in the input events flags.
See issues #4290 and #5172.
The idea is that these tests can be run with just a test server running
on a test host, with device under test connecting to it, instead of
requiring Internet connection for testing.
Such setup is however WIP, and some tests in net_hosted/ are so far
written to connect to Internet, as there're not test server written
yet. This is expected to evolve over time.
