Sync the test DB setup logic with upstream.

Reset password for the root user due to MariaDB 10.4 authentication
change.
https://mariadb.com/kb/en/authentication-from-mariadb-104/#altering-the-user-account-to-revert-to-the-previous-authentication-method

Relevant links:
ffdd8c6c67/tasks/rspec.rake (L37-L59)
https://github.com/brianmario/mysql2/blob/master/ci/setup.sh

rubygem-mysql2.spec

@@ -120,8 +120,15 @@ for i in $(seq 10); do
   echo "Waiting connections... ${i}"
 done
 
+# Reset password for the root user due to MariaDB 10.4 authentication change.
+# See https://mariadb.com/kb/en/authentication-from-mariadb-104/#altering-the-user-account-to-revert-to-the-previous-authentication-method
+mysql -u ${MYSQL_TEST_USER} \
+  -e "ALTER USER 'root'@'localhost' IDENTIFIED VIA mysql_native_password USING PASSWORD('')" \
+  -S "${MYSQL_TEST_SOCKET}" \
+  -P "${MYSQL_TEST_PORT}"
+
 # See https://github.com/brianmario/mysql2/blob/master/.travis_setup.sh
-mysql -u $MYSQL_TEST_USER \
+mysql -u root \
   -e 'CREATE DATABASE /*M!50701 IF NOT EXISTS */ test' \
   -S "${MYSQL_TEST_SOCKET}" \
   -P "${MYSQL_TEST_PORT}"
@@ -130,7 +137,7 @@ mysql -u $MYSQL_TEST_USER \
 cat <<EOF > spec/configuration.yml
 root:
   host: localhost
-  username: ${MYSQL_TEST_USER}
+  username: root
   password:
   database: test
   port: ${MYSQL_TEST_PORT}