A couple of test machines seem to have slow networking (?), so the remote eldap server initialization is aborted in init_per_suite

If underlying tcp connection is closed and LDAP operation returned tcp error,
then client applications tend to close ldap handle with eldap:close.
This will cause do_unbind to throw gen_tcp_error, which is unhandled
and will be sent to linked process as {nocatch, {gen_tcp_error, ...}}.
eldap should ignore gen_tcp_error during close, because it will be closing anyway.

As a first step to removing the test_server application as
as its own separate application, change the inclusion of
test_server.hrl to an inclusion of ct.hrl and remove the
inclusion of test_server_line.hrl.