Properly template the port number in config files with copy_setports.
The test takes two minutes on my machine which doesn't seem like a
proper justification to exclude it from the test suite, especially
considering we run these tests in parallel nowadays. The resource usage
doesn't seems significantly increased so it shouldn't interfere with
other system tests.
There also exists a precedent for longer running system tests that are
already part of the default system test suite (e.g. serve-stale takes
almost three minutes on the same machine).
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