net: dial tests are flaky on BSD

[bradfitz]

These have been flaking a lot on OpenBSD ...

https://storage.googleapis.com/go-build-log/f99ca413/openbsd-amd64-gce58_83506189.log

--- FAIL: TestDialTimeoutFDLeak (1.89s)
    dial_test.go:164: got 96; want >= 100
--- FAIL: TestDialerDualStackFDLeak (0.80s)
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
    dial_test.go:213: dial tcp 127.0.0.1:24574: i/o timeout
--- FAIL: TestReadUnixgramWithUnnamedSocket (0.19s)
    unixsock_test.go:60: read unixgram /tmp/go-nettest180765192: i/o timeout
--- FAIL: TestDialTimeoutMaxDuration (0.40s)
    timeout_test.go:140: #0: Dial didn't return in an expected time
FAIL
FAIL    net 12.082s

/cc @mikioh

[bradfitz]

Also on FreeBSD:

https://build.golang.org/log/73446e673c8f780dbfbc11aaab2b4f8e4daefb68

ok      mime/quotedprintable    0.156s
--- FAIL: TestDialerDualStackFDLeak (0.58s)
    dial_test.go:172: dial tcp: i/o timeout
    dial_test.go:172: dial tcp 127.0.0.1:59846: i/o timeout
    dial_test.go:172: dial tcp 127.0.0.1:59846: i/o timeout
    dial_test.go:172: dial tcp 127.0.0.1:59846: i/o timeout
    dial_test.go:172: dial tcp 127.0.0.1:59846: i/o timeout
    dial_test.go:172: dial tcp 127.0.0.1:59846: i/o timeout
    dial_test.go:172: dial tcp 127.0.0.1:59846: i/o timeout
FAIL
FAIL    net 2.256s
2016/05/11 17:45:36 Failed: exit status 1

@mikioh, @mdempsky, can one of you investigate?

[mdempsky]

Yeah, I'll look into the OpenBSD failures today.

[gopherbot]

CL https://golang.org/cl/23244 mentions this issue.