tests: Add fixture to have eddie-server running in background

Some integration tests or even units test with communication part we
might need to spin up a server for some particular test case and tear it
down again afterwards.

This commits shows an example how to implement this test fixtures in
ctest by using the FIXUP_SETUP/_CLEANUP properties on tests. The fixture
execution and teardown is handed over to scripts for tracking PID.

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>