Ensure socache_shmcb is enabled on all Apache 2.4 OSes

The SSLSessionCache option is specified as socache_shmcb, so the module must
be enabled.

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Feb 07 11:57:45 foreman-f19.example.com httpd[13215]: AH00526: Syntax error on line 11 of /etc/httpd/conf.d/ssl.conf:
Feb 07 11:57:45 foreman-f19.example.com httpd[13215]: SSLSessionCache: 'shmcb' session cache not supported (known names: ). Maybe you need to load the appropriate socache module (mod_socache_shmcb?).
</pre>