Remove IPv4 restriction for local_ip configuration statement.
Check for IP version mismatch of local_ip and remote_ip before creating
tunnel.
Create hash of remote IPv6 address for OVS interface/port name with least
posibility for collissions.
Fix existing tests that fail because of the added check for IP version
and subsequently valid IP addresses in _setup_tunnel_port.
DocImpact
Change-Id: I9ec137ef8c688b678a0c61f07e9a01382acbeb13
Closes-Bug: #1525895