Fix parsing of infra.mariadb.xinetd logs

Currently the logs tagged with infra.mariadb.xinetd flow into
elasticsearch with no hostname or programname attach, thus making
navigating the logs very hard.

The quick fix is renaming the tag to infra.mariadb-xinetd, which is just
enought to ensure the logs are processed correctly with the existing
filters.

TrivialFix

Change-Id: Icd72206de7c1f701bdf35c8fb3b128ef2dbe29a8