fix: make broker retry creating InfluxDB `db_test` database used for statistics

#70: test-asapo-broker-monitoring is regularly failing (see for example https://gitlab.desy.de/asapo/asapo/-/jobs/618331). When I investigated on my computer, it seems that the broker could not create the InfluxDB database db_test and therefore not publish any statistics to this database later.

This commit makes the broker retry to create the database during 10 seconds.