Currently the logging tests restore the "factory" logging configuration, not the actual one when the test was started.

Steps to reproduce: Enable '-b' (Debug flag) on the Pcap++ test executable. Observe how no debug logs are emitted after the logging tests finish.

Also, the logging test fails if the executable is started with '-b' flag.

Expected behaviour: The tests should restore the logging config as is was at the start of the test.

Additional note:
It might be a good idea to isolate the logging tests into a separate executable?