Improve timeouts when waiting for connections

`waitUntilConnected` is now checks for timeout *after* querying the
current number of connections, instead of before.

A test timeout was also relaxed.

This look into `waitUntilConnected` was prompted by the test failure in
https://travis-ci.org/programmiersportgruppe/akre/jobs/43482041
Remove hard-coded version number

This was prompted by sbt complaining that the core “test” configuration
wasn’t public and therefor couldn’t be used from other projects,
but it is probably the right thing to do anyway; we can supply the
version number in a release build with something like
`set version in ThisBuild = “x.y.z”`.