Moved disabling SSL verification from __virtual__() to get_conn()

__virtual__() is called once when the code is first loaded and won't
necessarily have the right context if there is more than one
configuration entry for the same provider.

All glory goes to @s0undt3ch for figuring out the problem.
Merge pull request #876 from whiteinge/fix-ssl-verify

Moved disabling SSL verification from __virtual__() to get_conn()
Adapt to the upcoming Salt `__virtualname__`  attribute.