Clean up configure.ac
Clean up configure.ac

Summary: Get rid of stuff in configure.ac that is now unused in mcrouter build process.

Test Plan:
Run `scripts/install_ubuntu_14.04.sh` on VM using new configure.ac.  Also, will
wait for Jenkins.

Reviewed By: pavlo-fb

Differential Revision: D2735097

fb-gh-sync-id: 2a2a539597930953d845c79db7312b74cf6460ca

facebook/mcrouter,nvaller/mcrouter,facebook/mcrouter,yqzhang/mcrouter,nvaller/mcrouter,yqzhang/mcrouter,synecdoche/mcrouter,yqzhang/mcrouter,synecdoche/mcrouter,yqzhang/mcrouter,synecdoche/mcrouter,facebook/mcrouter,synecdoche/mcrouter,facebook/mcrouter,nvaller/mcrouter,nvaller/mcrouter