Alert emails use localhost and loopback address which is useless

The alert emails are sent from couchbase@localhost to root@localhost with a generic body as

Approaching full disk warning. Usage of disk "/opt/couchbase/var" on node "127.0.0.1" is around 92%.

When the recipient is changed to a group of individuals, they receive an email without giving them any indication on which server the problem has happened . Currently, we're working around this by changing the sender address to couchbase@myserver.mydomain.com but this doesn't change the body and shouldn't be necessary.

This ticket is to change the email sender and body to include the hostname and IP.