Make nodetool command work with ipv6 nodes

nodetool appears not to handle ipv6 addresses properly.
Patch submitted:
https://issues.apache.org/jira/browse/CASSANDRA-7669

In the mean time, ccm can use 'localhost' in the nodetool commmand. This
allows the nodetoll jmx url to format properly, and the address to
resolve.
*CAVEAT: user must have <ip> localhost entires in their 'hosts' file for
any node to be commanded.
Merge remote-tracking branch 'upstream/master' into ipv6-support
Adding support for IPV6 addresses

- new ipformat argument for supporting link-specific addresses
    --ip-format='fe80::1%lo0'
- existing api default functionality unchanged
- common.check_socket_available now works with ipv6 addresses
- ipv6 addresses are expanded to match host format from cassandra

also fix arbitrary typo in common.parse_settings
Break after replacing IPv4 option once
Guard against None itf in normalize_interface
simplify zeros string generation in normalize_interface
Merge remote-tracking branch 'upstream/master' into ipv6-support

Conflicts:
	ccmlib/common.py
Merge pull request #143 from aholmberg/ipv6-support

Ipv6 support