mod_ssl: Fix "SNI for backend" when compiled against

OpenSSL without support for SSLv2.

PR 55194.

Followup to r1497466. Does not apply to trunk or 2.4.x.

Proposed by: rjung
Reviewed by: covener, trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1500108 13f79535-47bb-0310-9956-ffa450edef68