sslutil: don't attempt to find default CA certs file when told not to Before, devel.disableloaddefaultcerts only impacted the loading of default certs via SSLContext. After this patch, the config option also prevents sslutil._defaultcacerts() from being called. This config option is meant to be used by tests to force no CA certs to be loaded. Future patches will enable _defaultcacerts() to have success more often. Without this change we can't reliably test the failure to load CA certs. (This patch also likely fixes test failures on some OS X configurations.)