SPARK-2879 part 2 [BUILD] Use HTTPS to access Maven Central and other repos

.. and use canonical repo1.maven.org Maven Central repo. (And make sure snapshots are disabled for plugins from Maven Central.)

Author: Sean Owen <srowen@gmail.com>

Closes #1828 from srowen/SPARK-2879.2 and squashes the following commits:

639f495 [Sean Owen] .. and use canonical repo1.maven.org Maven Central repo. (And make sure snapshots are disabled for plugins from Maven Central.)
(cherry picked from commit 75993a65173172da32bbe98751e8c0f55c17a52e)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>