Allow using Browsermob server in parallel

[abotalov]

Merry Christmas 🎄 🎅 🎁

[abotalov]

The tests fail in 1.9.3 when at_exit hook is NOT invoked (i.e. when server isn't stopped). For some reason it stucks after calling exit in forked process.

I don't know why it happens.

It works in 2.0 and 2.1.0

[abotalov]

I asked a question on Stackoverflow about this issue - http://stackoverflow.com/questions/24271717/process-stucks-when-invoke-childprocess-from-a-forked-process-in-ruby-1-9-3. Do you know the answer?

[abotalov]

I fixed it according to your SO answer. The build failures seem to be unrelated.