Fix loading SSL Context when certpaths not exist in configuration

- Make cert paths field optional in configuration.
- Allow to skip ssl context load.
- Make PublisherConfig and SubscriberConfig fields optional.
- Remove Auth Header when AAF credentials are empty

Issue-ID: DCAEGEN2-3032
Issue-ID: DCAEGEN2-3038
Signed-off-by: Tomasz Wrobel <tomasz.wrobel@nokia.com>
Change-Id: I27d44cf8c2887b3a75c5ad16f833439b7b5757ee
28 files changed