Add test for sethostname() and friends

This test can run on both Linux (needs root permissions) and OSv.

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
modules: make api.require() impose compilation ordering

This change makes api.require() express not only run-time dependency
but also imply a compilation order. osvinit depends on httpserver
artifacts during its build, require() could be reused in a simple way
to express this dependency.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>