Make service tests packaging consistent

core/src/test/java/cz/muni/fi/pa165/core/flight/FlightServiceImplTests.java → core/src/test/java/cz/muni/fi/pa165/core/service/flight/FlightServiceImplTests.java

-package cz.muni.fi.pa165.core.flight;
+package cz.muni.fi.pa165.core.service.flight;
 
 import cz.muni.fi.pa165.core.data.domain.Flight;
 import cz.muni.fi.pa165.core.data.repository.flight.FlightRepository;

core/src/test/java/cz/muni/fi/pa165/core/steward/StewardServiceImplTests.java → core/src/test/java/cz/muni/fi/pa165/core/service/steward/StewardServiceImplTests.java

-package cz.muni.fi.pa165.core.steward;
+package cz.muni.fi.pa165.core.service.steward;
 
 import cz.muni.fi.pa165.core.data.domain.Flight;
 import cz.muni.fi.pa165.core.data.domain.FlightSteward;