fix http 502 (bad gateway) after running 'vagrant provision' twice

I've seen a couple of those and managed it to track down to
pecl install xhprof (as it seems). php5-fpm does get an
SIG SEGV after installing this for the second time.
notify php5-fpm after installation of xhprof

this should make commit 2b1b1af8ae7a821a6696e19ea92fcc6498132487 more or less useless.