Remove logging in __virtual__ func.

With default settings.

Before:
```bash
(salt)root@master:~# salt-call --local test.version
[INFO    ] Package debconf-utils is not installed.
[INFO    ] Package debconf-utils is not installed.
local:
    0.17.0-4831-g43ec66d
```

After:
```bash
(salt)root@master:~# salt-call --local test.version
local:
    0.17.0-4831-gd7e5346
```