Automatic merge from submit-queue

Make local-up-cluster.sh IPv6 friendly

Added a new environment variable `API_HOST_IP`. `API_HOST_IP` allows the
user to specify an IPv6 address that is parsable by Golang. `API_HOST` on
the other hand allows the user to specify the IPv6 address to be used in
a URL's format as described in RFC2732.

Example:
```bash
API_HOST_IP="FEDC:BA98:7654:3210:FEDC:BA98:7654:3210"
API_HOST="[FEDC:BA98:7654:3210:FEDC:BA98:7654:3210]
```
or
```bash
API_HOST_IP="FEDC:BA98:7654:3210:FEDC:BA98:7654:3210"
API_HOST="[${API_HOST_IP}]"
```
Signed-off-by: André Martins <aanm90@gmail.com>