These tests are fundamentally racy, removing to improve reliability of
test cases.

When config dir is mounted from configmap, filepath.Walk() finds the same
.conf file twice as 20-acme.conf is a link to ..data/20-acme.conf for example.

This patch skips all folder names starting with '..' which is pretty
uncommon and mainly used by Kubernetes mounts.

By the time the aggregator.run() was called about 600ms already passed since setting now which was skewing up the aggregation intervals and skipping metrics.

Fixes issue where metrics collected immediately after startup would not
be aggregated.

This prevents a pattern with no wildcards from matching in case
permissions is denied.

Adjust logic in functions responsible for passing metrics in order to be able
to process them correctly in case where pass and drop are defined together.

Looping the metrics back through the same channel could result in a
deadlock, by using a new channel and locking the processor we can ensure
that all stages can make continual progress.

It is not possible to encode a measurement, tag, or field whose last
character is a backslash due to it being an unescapable character.
Because the tight coupling between line protocol and the internal metric
model, prevent metrics like this from being created.

Measurements with a trailing slash are not allowed and the point will be
dropped.  Tags and fields with a trailing a slash will be dropped from
the point.

closes #2466

fixes #2380

fixes #2317