Tests: investigate failing unit tests on iOS

[orangemocha]

These tests fail consistently on both iOS 9 and 10, using our new test app, and need to be investigated.

Test	iOS 9.3	iOS 10.2	Symptom	Reason
test-http-client-pipe-end.js	fail	fail	pipe EADDRINUSE	unknown
test-http-client-response-domain.js	fail	fail	pipe EADDRINUSE	unknown
test-http-unix-socket.js	fail	fail	pipe EADDRINUSE	unknown
test-net-pingpong.js	fail	fail	pipe EADDRINUSE	unknown
test-net-pipe-connect-errors.js	fail	fail	pipe EADDRINUSE	unknown
test-pipe-address.js	fail	fail	pipe EADDRINUSE	unknown
test-pipe-stream.js	fail	fail	pipe EADDRINUSE	unknown
test-pipe-unref.js	fail	fail	pipe EADDRINUSE	unknown
test-repl.js	fail	fail	pipe EADDRINUSE	unknown
test-tls-connect-pipe.js	fail	fail	pipe EADDRINUSE	unknown
test-fs-watch.js	fail	fail		unknown
test-module-loading.js	fail	fail		unknown
test-tls-fast-writing.js	fail	fail	crash! Assertion failed: (buf.base != NULL), function uv__read, file ../deps/uv/src/unix/stream.c, line 925	unknown
test-http-upgrade-server2.js	fail	fail		unknown
test-next-tick-starvation.js	fail	fail		unknown
test-path.js	fail	fail		uses absolute paths

The ones that say "pipe EADDRINUSE" all seem to fail for the same reason.