SDK4: macOS x86: tcp connections are not closed

Using the python client 4 on macOS x86, tcp connections are not closed leading to performance degradation and file descriptor exhaustion.

./u_test_5.py --host 10.28.1.220 --cycles 25

==> Attempt 25:
Creating bucket
Creating index
Upsert 100 test docs
Getting test docs
open: 0 connections: 52 fds: 59 children: 0 ESTABLISHED: 52 
====> done <====
Success.

Same test program on Linux:

==> Attempt 25:
Creating bucket
Creating index
Upsert 100 test docs
Getting test docs
open: 0 connections: 4 fds: 12 children: 0 ESTABLISHED: 4
====> done <====
Success.