Potential fix for #1557
closing() the worker_pool
More work related with #1557, now avoiding the issue with close() dead-lock
Cosmetic, S in the result is more visible and I'll know something is "wrong"
Test case which reproduces Pseudo-random number of vulnerabilities found in audit phase (xss) #1557
Minor bugfix
Added timeout for Pool.finish method
Merge branch 'develop' of git://github.com/andresriancho/w3af