Previously, flags would be compared in the exact order they are output
by MySQL, which can result in false negatives if the input ordering does
not match.
Example from the ticket:
```
[root@avvr-dbm51 ~]# pt-config-diff /etc/my.cnf h=localhost,P=3047
1 config difference
Variable /etc/my.cnf avvr-dbm51
========================= ============ ============
myisam_recover_options FORCE,BACKUP BACKUP,FORCE
```
This commit fixes the issue by sorting the flags before comparison to
ensure that any ordering differences will not report a diff.
Co-authored-by: Jonathan Gnagy <jonathan@therubyist.org>
