net: do not inherit the no-half-open enforcer

[lpinca]

Socket.prototype.destroySoon() is called as soon as UV_EOF is read
if the allowHalfOpen option is disabled. This already works as a
"no-half-open enforcer" so there is no need to inherit another from
stream.Duplex.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

net