Check process list if ekapeli is running, instead of using flock.
Necessary for case where there might be two or more games
running as different users on the same server (the previous hack
prevented this from happening).
Create a temporary directory properly for Ekapeli.
Avoid possible problems with persistancy (".cow" was shared
between invocations of Ekapeli, and previous runs could affect
future runs).  Plus using "mktemp -d" is more secure.
Do clean up the temporary Ekapeli directory after we have done
using it.