Revert "BUG-635: implement MD5 auth option for BGP peers"

This reverts commit b40afa455f9d1898c8a1ed07b05220c5a3d68d31.

Change-Id: Ifbe47173d234819512b6c08b1e2e5a31b877e98f
Signed-off-by: Robert Varga <rovarga@cisco.com>