BUG-634: Fix JNI bugs

This patch fixes issues discovered while implementing testcases:

- Fix handlers not being retained
- Fix failure to lookup LoggerFactory.getLogger()
- Remove getsockopt(TCP_MD5SIG), as it is not implemented in Linux
- Fix key removal mechanics
- Make sure struct tcp_md5sig contains the address

Change-Id: Id7185a33d00e794c9c2bfa1a7c4a9bf685a2ed59
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-634: Fix JNI bugs"