Remote config loading code could be more clear

Small code quality issue, the code is currently a bit harder to follow than feels necessary:
https://github.com/Graylog2/collector/blob/044b82868894e0dea5408d976cd06a1612be9502/superv/configmanager/manager.go#L276-L307

Start by reading superv/configmanager/manager.go at lines 276-307, the only location identified in the issue, and trace the remote config loading flow around it. Clarify the control flow without changing its behavior, then verify that remote config loading still works as before.

Written by the indexing model from the issue text.