x/net/http2: TestServer_Rejects_TLSBadCipher fails on OpenBSD arm

[andybons]

Example from https://build.golang.org/log/791d55e2cf7e2f96ac6ad20f561477a0f401c861

See https://build.golang.org/?repo=golang.org%2fx%2fnet for more instances

--- FAIL: TestServer_Rejects_TLSBadCipher (0.05s)
    server_test.go:549: got a *http2.SettingsFrame; want *GoAwayFrame
    server_test.go:235: Framer read log:
        2019-08-21 14:37:42.791078336 Framer 0xc29d80: read SETTINGS len=24, settings: MAX_FRAME_SIZE=1048576, MAX_CONCURRENT_STREAMS=250, MAX_HEADER_LIST_SIZE=1048896, INITIAL_WINDOW_SIZE=1048576
FAIL
FAIL	golang.org/x/net/http2	74.768s

@FiloSottile