net: do not set V4MAPPED on FreeBSD
AI_V4MAPPED is not supported on FreeBSD. This was originally fixed in 04bea9f9. However, a possibly better alternative just landed in https://github.com/joyent/node/commit/0e392f3b68fecf8d45032a8f427e22f7f1cb25cf. This commit reverts 04bea9f9 and applies https://github.com/joyent/node/commit/0e392f3b68fecf8d45032a8f427e22f7f1cb25cf.
The original fix unsets the flag during DNS lookup on FreeBSD. The new, alternative approach, does not set the flag in the first place in connect()
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R=@indutny