Fixed pipe name conflict

I fixed the "existing pipe" issue. I use `mktemp` to generate a unique file name, then I use `mkfifo` to make a pipe with this name. I opted to store the temp pipes in a local directory. The function`mktemp`, by default, saves its files to the `/tmp/` folder. Someone can modify the `/tmp/` folder and its contents while rapache is running, so I figured this was unsafe. The temp folder I made is created only when the script is running, and deleted when it ends.