Add support for OS-specific CA bundle locations

GitHub pull: #19
Suggested-by: Michael Vogt <mvo@ubuntu.com>
Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>
Merge commit '818486283ed2ccf55e9a0d6be8a1acd8727fb69e'

Testing in "next" revealed no problems (yet).

Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>