MaxClientsAllowed still behaves incorrectly when the connections are full and open connections take longer than one minute to shutdown

[amoerie]

Describe the bug
DICOM server stops accepting incoming connections if MaxClientsAllowed is used, connections are full and existing connections take longer than one minute to disconnect.

To Reproduce
I will write a test to prove my theory

Expected behavior
DICOM server should always accept up to MaxClientsAllowed connections

Screenshots or test DICOM files

Environment
Fellow Oak DICOM version: latest
OS: any
Platform: any