Missed config keys on Scala 2.13.x

[joni-jones]

The origin of the issue is iteration through the config keys here and here and at the same time properties change in the loop which can lead to skipping some keys after +=.

Fixed an issue with missed config keys while iterating through them on Scala 2.13.x
!Note: This issue reproduces only on Scala >= 2.13.x version and probably related to some internal changes in Scala.