Add logging for BGP Config module.

Modify bgp_config_test so that BgpConfigManagerTest does not result
in creation of any operational structures even though we have a BGP
Server.  This is done by unregistering the observers for the config
from the test setup code.
Split BgpConfigManagerTest and BgpConfigTest into separate files.
Merge pull request #110 from Juniper/nsheth_config_log

Add logging for BGP Config module.