9.16.21 Regression: Legacy check-names configuration does not work anymore

In 9.16.21 a legacy configuration with check-names master ... or check-names slave ... does not work anymore. The initial commit supporting the new syntax in dca36587 added a fallback to master/slave, if the no configuration for primary/secondary exists.

A recent change in fb88554b changed the default config to use the new configuration names. This causes, that the fallback is never used, because there always exists a configuration for primary and seconday (even if the user config is using the old names). So every user configuration with check-names master ... and check-names slave ... is now ignored!

A simple solution to not break old user configurations, would be to swap the order of the named_checknames_get calls and first check for master/slave and only fallback to primary/secondary.