test: Don't reuse common.PORT in test-child-process-fork-net
test: Don't reuse common.PORT in test-child-process-fork-net

This fixes #3447

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node