Synchronize db before server listen

[glebec]

There is a race condition in the server start; it listens on a port without waiting for the database to finish syncing. While this almost certainly will not cause any problems in practice (how often does a request come in during the interval between starting the server and the db syncing?), it will be easy enough to implement the fix and demonstrate good practices.

[glebec]

Closing following comments in https://github.com/FullstackAcademy/bones/issues/64.