Implement/test support for KV with homogenous IPv6

If I put some ipv6 address (for example "::1") function lcb_host_parse(...) returns LCB_INVALID_HOST_FORMAT error.
It is needed to add ipv6 support

This aligns to what we're calling phase one in the CBD. Note that it need not merge into the master branch for the next micro if there is concern about introducing instability, but does need to be identified on a topic/branch in that case.  Adjust the fix version as appropriate.