866493 - frequent SSL renegotiations and log level

Until now, Katello had configured client certificates for /katello path
while we need this only for /katello/api path (and /subscription for newer
rhsm clients).

This was leading to many errors for each UI request when browser was
apparently not sending any client certificate. Together with way too verbose
log level (info instead of the default warn) this was resulting to about
20-30 log lines for each UI request.

This patch moves the client certificate configuration only in /katello/api
location leaving the /katello location configuration empty now.

It also sets warn default log level.

https://bugzilla.redhat.com/show_bug.cgi?id=866493
Merge pull request #1562 from lzap/ssl-errors-httpd

866493 - frequent SSL renegotiations and log level