crypto/tls: TestVerifyHostnameResumed consistently failing in longtest builder

[bcmills]

crypto/tls.TestVerifyHostnameResumed is consistently failing in the linux-amd64-longtest builder.

First failure was at CL 184099, which appears to be unrelated. That suggests some sort of change in a non-hermetic dependency, or perhaps in the builder itself.

Example: https://build.golang.org/log/67d2b12bec6bf70eb818bb3246aee32990ecd9e6

--- FAIL: TestVerifyHostnameResumed (0.10s)
    --- FAIL: TestVerifyHostnameResumed/TLSv12 (0.05s)
        tls_test.go:383: Subsequent connection unexpectedly didn't resume
    --- FAIL: TestVerifyHostnameResumed/TLSv13 (0.05s)
        tls_test.go:383: Subsequent connection unexpectedly didn't resume
FAIL
FAIL	crypto/tls	0.828s

CC @agl

[dmitshur]

I can reproduce this on macOS with Go 1.12.6.

~ $ go version
go version go1.12.6 darwin/amd64
~ $ go test -count=1 crypto/tls
--- FAIL: TestVerifyHostnameResumed (1.62s)
    --- FAIL: TestVerifyHostnameResumed/TLSv13 (0.55s)
        tls_test.go:392: Subsequent connection unexpectedly didn't resume
FAIL
FAIL	crypto/tls	2.943s

[gopherbot]

Change https://golang.org/cl/186239 mentions this issue: crypto/tls: remove TestVerifyHostnameResumed

[gopherbot]

Change https://golang.org/cl/186277 mentions this issue: [release-branch.go1.12] crypto/tls: remove TestVerifyHostnameResumed

[gopherbot]

Change https://golang.org/cl/186279 mentions this issue: [release-branch.go1.11] crypto/tls: remove TestVerifyHostnameResumed