Log the CA cert with the debug statement

If you are using a custom CA bundle rather than the default OS one then
we should log that as part of the curl statement to make debugging
easier.

Change-Id: I1a6ded02b75a3bc9b1ca880db8a9b9b460d36774
Expose version matching functions to the public

The functions to match a version or convert a string version number into
a tuple have shown to be useful in at least auth_token middleware. I
think this is also better as _discover should really only be a shadow
for the discover file because of the circular dependency problems.
_discover shouldn't really need to be used even within client.

Closes-Bug: #1400998
Change-Id: Icf700c30d01e0700e437437a23e63a7f100ce4d3
Merge "Expose version matching functions to the public"
Merge "Log the CA cert with the debug statement"