ScanManagers, ScanResultProcessors: don't call non-thread-safe code from a thread

Excessive usage of direct Qt connections lead to a large amount of code
in various ScanResultProcessors being called from a non-main thread, but
the result processors didn't expected it, weren't thread-safe, which
lead to data races.

This fixes one confirmed crash and may fix more seemingly random Local
Collection updating behaviour.


FIXED-IN: 2.8