Default to utf8 for MySQL

Change default charset to utf8 and default collation order to
utf8_unicode_ci to align with upstream defaults.

Change-Id: I0fb57f14a0d30226c840a6e920f2b3807b90080a
Closes-Bug: #1322715
(cherry picked from commit 166b00a773bb2830175bd61a451294d757453eb3)