Fix "Problem with the SSL CA cert" issue @
https://github.com/google/edash-packager/issues/6. On Ubuntu, CURL_CA_BUNDLE
is located at "/etc/ssl/certs/ca-certificates.crt" while on CentOs, it is
located at "/etc/ssl/certs/ca-bundle.crt".
With this change, GYP scans the common appearing locations for SSL CA cert.
Change-Id: I838bae3954ec51f1430c900d1e82596d45a4db84