cluster/message: added a test for issue 5330

There is a race condition in Node v0.10 that crashes a worker when
receiving a message while starting listening to a port.
This commit adds a test to try to detect this bug.
cluster/message: modified test-cluster-message-2

test-cluster-message-2 now uses common.PORT
test/simple: cluster/message -> no real need for 1000ms timeout

Reduced the setTimeout from 1000ms to 50ms as it is not needed to
wait so long for this test.
test: cluster/message: added another test for issue 5330

Added another test for issue 5330 that sends sockets handles
to the master process. It crashes on Linux with Node v0.10.
test: cluster/message: improvements after reviews

Improved test-cluster-message-{1,2} to be compliant with reviews
test: cluster-disconnect increased workers to 8

Increasing the number of workers from 2 to 8 makes this test
harder against race conditions.

For example, it could trigger more easily the issue 5330.