Fix broken 'dovecot' git submodule dependencies

1) Fetch EthACKdotOrg/dovecot for via HTTPS to avoid authenticity errors
with some github.com ip addresses:

```
Cloning into 'puppet/modules/dovecot'...
The authenticity of host 'github.com (192.30.252.128)' can't be
established.
RSA key fingerprint is 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48.
Are you sure you want to continue connecting (yes/no)? ^C
fogmail (master)$ Clone of 'git@github.com:EthACKdotOrg/dovecot.git'
into submodule path 'puppet/modules/dovecot' failed
```

2) Fix referred commit for EthACKdotOrg/dovecot (previous commit was probably squashed when feature branch was rebased for https://github.com/mjhas/dovecot/pull/27)

---

:fish_cake: **Bonus Question:** are you open to switch to a puppet module dependency manager, instead of relying on git submodules? I am a total newbie in Puppet (but have some experience with Chef and Ansible CM tools) and with rapid internet search it seems to me that http://librarian-puppet.com/ would be a (the) good candidate.