Follow up to r1750392: r1756186 should have also bumped MMN minor for

s/ap_proxy_check_backend/ap_proxy_check_connection/, and r1756328 really bump the MMN :p

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1756329 13f79535-47bb-0310-9956-ffa450edef68