test: use dynamic port in test-dgram-bind-shared-ports
Use of common.PORT in parallel tests is not completely safe (because the same port can be previously assigned to another test running in parallel if that test uses port 0 to get an arbitrary available port).
Remove common.PORT from test-dgram-bind-shared-ports.
Refs: https://github.com/nodejs/node/issues/12376
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
test