[generator.c.tests] fix race conditions traceTest and tcpTest (no runtime changes)

This is an alternative fix for tcpTest, instead of MR !34 (closed).

The difference is, this works around the lack of synchronization with the server start listen function by just using a retry strategy in the test. This avoids introducing extra synchronization and lifecycle stuff in the runtime implementation for this one corner case.

(Note: the fix for traceTest is the same as in MR !34 (closed), just rebased)

Issue #74 (closed)