mod_ssl: follow up to r1734561 and r1735337.

We also need to reset the X509_STORE_CTX's error in the callback to quiet
X509_V_ERR_UNABLE_TO_GET_CRL for the leaf certificate (caught by AH02010).



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1737265 13f79535-47bb-0310-9956-ffa450edef68