Fix intermittent test failure in starting/stopping apps
Fix intermittent test failure in starting/stopping apps

Lifecycles of exometer_cache table and probe process are incompatible
(probe may outlive cache) hence remove custom usage of cache in probe.

This was happening very seldomly in tests stopping exometer_core.  It
may have happened when stopping real node too (though harmless).

aeternity/epoch,aeternity/epoch,aeternity/epoch,aeternity/epoch