[php-maint] Bug#626640: Small optimization

[Marcus Cobden]

Here's (what I hope is) a small optimisation to Bob's solution.

* fuser returns non-zero if the files aren't in use
* since we only need the argument once, we probably don't need a shell

Can you guys check this over for me?

find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f \
	-cmin +$(/usr/lib/php5/maxlifetime) \
	! -execdir fuser -s {} \; \
	-delete