add mysql and sqlite3 default test

[kenjiszk]

Summary

Extend database default value test for mysql and sqlite3.

Other Information

MySQL text type cannot be assigned a default value. So it is skipped.
http://dev.mysql.com/doc/refman/5.6/en/data-type-defaults.html

[rails-bot]

Thanks for the pull request, and welcome! The Rails team is excited to review your changes, and you should hear from @rafaelfranca (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[rafaelfranca]

MySQL tests are broken.

[kenjiszk]

@rafaelfranca
I changed the order of base_test, then test recovered. Is there test execution order in active record test? or Am I doing some wrong cording?

[arthurnn]

can you also test if this works with: bin/test -a mysql2

[kenjiszk]

@arthurnn @rafaelfranca
Thank you for comment. I have revealed the cause issue. The test of "schema_dumper_test.rb" created and dropped a "defaults" table and it affect on test of "base_test.rb". So, it was succeeded when changing test order. I change table name of schema dump test from "defaults" to "dump_defaults". Could you please check this?

[arthurnn]

do you mind rebasing this, and I will give it a final look and 🍏 it