[bug] Deno.utime

[zekth]

As explained in denoland/std#421
Deno.utime seems buggy on MacOs.

Loss of precision when changing timestamps using Deno.utime

cc @axetroy

example:

test [fs] copy synchronously with preserve timestamps ... ‌FAILED‌
Error: 

    ‌[Diff]‌ ‌Left‌ / ‌Right‌


-   1558364063‌
+   1558364062‌

    at assertEquals (/Users/vsts/agent/2.150.3/work/1/s/testing/pretty.ts:66:11)
    at assertEquals (/Users/vsts/agent/2.150.3/work/1/s/testing/asserts.ts:64:5)
    at /Users/vsts/agent/2.150.3/work/1/s/fs/copy_test.ts:185:5
    at fn (/Users/vsts/agent/2.150.3/work/1/s/fs/copy_test.ts:32:13)
    at runTestsSerial (/Users/vsts/agent/2.150.3/work/1/s/testing/mod.ts:112:19)
    at async runTests (/Users/vsts/agent/2.150.3/work/1/s/testing/mod.ts:147:9)
    at async main (/Users/vsts/agent/2.150.3/work/1/s/testing/main.ts:5:5)