mod_ssl: Fix potential SSL I/O filter hang if a long list of

trusted CAs is configured for client cert auth.  PR 46952
+1: jorton, wrowe [from review of svn patch], minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@917343 13f79535-47bb-0310-9956-ffa450edef68