Improve Config Files (followup from capabilities)

[morgo]

This is a followup to #4987

It cleans up the config files and renames them into a convention that makes more sense for the current usage. It also fixes test/local_example.sh to use etcd2 as the tutorials on vitess.io have switched to it.

Full config changes:

• Only sets a setting once (so if it is in global.cnf it won't be in a per-version file and vice versa)
• Stops setting settings to the default value (so if a default value changes to be what was intended in 8.0, I will not put the value in global.cnf. It will be specified in each per-version config except 8.0)
• Changes to have only global.cnf and one per-version config file (this changes behavior from PR#4987 slightly, but makes config files easier to follow).
• If MySQL 8.0 prefers binlog_expire_logs_seconds, make sure it doesn't set expire_logs_days (causes a warning)
• Make sure MySQL 8.0 uses the default utf8mb4 character set.
• Make sure that MySQL flavors use their default SQL Mode as long as it is STRICT.
• Remove MYSQL_FLAVOR boilerplate from bootstrap.sh
• Remove MYSQL_FLAVOR ENV from all docker files
• Rename default-fast.cnf to testsuite.cnf (It could be misinterpreted - this is not fast, its testsuite with unsafe settings)
• Make sure defaults don't have anything unsupported just so the testsuite passes (looking at you SBR, which is later changed by including a file)
• Remove unused config files.
• Rename config files from master_*.cnf to *.cnf since the config files do not need to be different between master and slave.
• Rename rbr.cnf to testsuite-rbr.cnf and only include when the testsuite requires it (this is different from the previous usage where all usages required it. Now the per version files always set RBR and never SBR).

One change that it doesn't make, is that the Python default MYSQL_FLAVOR is still MariaDB. When I changed this to MySQL56 the testsuite wouldn't pass (it failed in local_example trying to download maven files). This will have to be looked at as a followup.

Signed-off-by: Morgan Tocker tocker@gmail.com