It appears that when requesting multiple ports asynchronously,
that a port is given out multiple times, which crashes single
Tor processes. Such a crash brings down the whole system as of
now, which might or might not be desired.
This is caused by a race condition on the port numbers. This
commit fixes the issue if a number of Tor instances for the pool
is requested. If the pool is populated with an array of definitions,
the user has to make sure to include the ports in the definition,
otherwise the race condition still persists. If this should still be
allowed is up for discussion or if a check should be included in the
TorPool create function.
