commit 32d52f344aa564154b96cadc2dda3f0de3d0f455
author Jerry Wong <jpwong@broadcom.com> Tue Oct 06 22:18:11 2015 -0700
committer Erik Kline <ek@google.com> Sat Oct 17 03:36:32 2015 +0900
tree 9097a097156ba5ceaff46eeb8aa3d9c46ac52df3
parent beecb61554b5f55fd4ec2da945328eefb918b4e1

Incorrect time used in some NTP server responses

Per RFC 4330, a NTP server response should be discarded when:
    - the stratum is 0 (unspecified), or
    - the leap indicator is 3 (unsync'ed), or
    - the mode is not 4 (server) / 5 (broadcast), or
    - the transmitted time is 0.

Update SntpClient so that such responses would be discarded.

Additionally:
    - make some variables suitably "final"
    - enable logging
    - add alternate requestTime() for testing
    - add some miniscule test coverage

Cherry-picked from Jerry Wong's

    https://partner-android-review.googlesource.com/#/c/460074

Bug: 24719581
Change-Id: Id11a79a6e53ce95500ed4b4d691a29c260666f6c