TestHttpsInsecure failures on certain darwin builders

[ALTree]

We're getting TestHttpsInsecure failures on some (but not all) of the darwin builders.

OSX 10.11 and 10.12 are fine.
The OSX 10.8 and 10.10 builders fail. The darwin-arm-a1549ios builder is also failing.

This is the OSX error:

--- FAIL: TestHttpsInsecure (10.04s)
	fetch_test.go:305: grabProfile(https+insecure://127.0.0.1:59997/debug/pprof/profile) got PeriodType: cpu nanoseconds
		Period: 10000000
		Time: 2017-06-20 11:36:19.953808169 -0700 PDT
		Duration: 10.0
		Samples:
		samples/count cpu/nanoseconds
		        492 4920000000: 1 2 3 4 5 6 
		Locations
		     1: 0x105efd3 M=1 runtime.kevent /var/folders/6g/8k13h11n2zb8hxx99wk6f6y40000gn/T/workdir/go/src/runtime/sys_darwin_amd64.s:526 s=0
		     2: 0x102a672 M=1 runtime.netpoll /var/folders/6g/8k13h11n2zb8hxx99wk6f6y40000gn/T/workdir/go/src/runtime/netpoll_kqueue.go:79 s=0
		     3: 0x103405a M=1 runtime.findrunnable /var/folders/6g/8k13h11n2zb8hxx99wk6f6y40000gn/T/workdir/go/src/runtime/proc.go:2099 s=0
		     4: 0x10349eb M=1 runtime.schedule /var/folders/6g/8k13h11n2zb8hxx99wk6f6y40000gn/T/workdir/go/src/runtime/proc.go:2237 s=0
		     5: 0x1034d05 M=1 runtime.park_m /var/folders/6g/8k13h11n2zb8hxx99wk6f6y40000gn/T/workdir/go/src/runtime/proc.go:2300 s=0
		     6: 0x105aeda M=1 runtime.mcall /var/folders/6g/8k13h11n2zb8hxx99wk6f6y40000gn/T/workdir/go/src/runtime/asm_amd64.s:286 s=0
		Mappings
		1: 0x0/0x0/0x0   [FN]
		, want function "TestHttpsInsecure"
FAIL
FAIL	cmd/vendor/github.com/google/pprof/internal/driver	10.545s

Full logs: OSX 10.10, OSX 10.8, iphone6. The last one is a little different.

[aalexand]

@nolanmar511 as part of investigating / fixing this, we should make our travis tests run with several OSX versions, I'll file an issue on this.

[aalexand]

This issue blocks golang/go#21047.

[aalexand]

I wonder if the failure is related to golang/go#13841.