SessionHandlerMemcache: Simplify session store.
SessionHandlerMemcache: Simplify session store.

This patch lays the groundwork for removing the MemcacheStore class later.

madmatt/saml2,sitya/saml2,simplesamlphp/saml2,ArtemTeleshev/php-saml2,sgomez/saml2,newmen/saml2,cb8/saml2