TLS tests for Restconf Northbound interface

TLS tests for Restconf Northbound interface

Support for configuring, activating and executing HTTPS requests towards
northbound interface provided by Jetty.
Note for activating certaing configurations it is required to restart
ODL completely by means of Karaf command: shutdown -r

For reloading certificate information (keystore/trustore) it is only
required to restart jetty bundle. Note this operation is not supported
officially for production environments.

These tests are based on openssl/keytool external commands.

Change-Id: I21b2d2f60d65a04342ef6d1de882c2b59915f40b
Signed-off-by: Miguel Angel Munoz Gonzalez <miguel.angel.munoz.gonzalez@ericsson.com>