Fixing select service in return medecines module

[mbayopanda]

This PR fixes the Return distribution from service module.

To run correctly the app, please :

• Don't use STRICT_ALL_TABLES mysql mode
• Use the external file db.sql
• Then execute the /server/models/update/synt.sql file

NOTA: The exchange rate module doesn't have a bug when we try to define a new exchange rate when we are not in STRICT_ALL_TABLES mysql mode

[mbayopanda]

@DedrickEnc please merge this PR as soon as possible