Fixed inline call to `lsb_release` in command to add APT Basho repository

Fixed inline call to `lsb_release` in command to add Basho repository to APT sources list.

```bash
hector@eazy-e:~$ lsb_release -sc
precise
hector@eazy-e:~$ bash -c "echo deb http://apt.basho.com $(lsb_release -sc) main"
deb http://apt.basho.com precise main
```

Credit goes to `flazz` in IRC for identifying this issue.