tests: Adjusted files not directly related to tests

`tls.bash` helper was adapted to the new helper scripts location. The `setup.bash` helper saw a bugfix (expanding the array properly) and updates the container default config to configure for IPv4 explicitly.

The IPv4 default was added after recent Docker pushes and I saw weird IPv6 related errors in the logs.. now we're sure IPv4 is the default during tests.

Added functionality to check if a process is running:
- This change adds a helper function to check whether a program is running inside a container or not.
- This added the need for a function like `_run_in_container` but allowing for providing an explicit container name.
- Future PRs can use this helper function now to check whether a process is running or not. This was done for the tests of Fail2Ban, but can be used for other tests in the future as well.

---

chore: Restructured BATS flags in `Makefile`

The `Makefile` has seen a bit of a restructuring when it comes to flags:

1. The `MAKEFLAGS` variables is used by `make`, and allows for adding additional flags that can be used within in recursive calls (via `$(MAKE)`) too,  thus DRY approach.
2. The flags for calling BATS were adjusted. `--no-parallelize-within-files` has been added as well to ensure tests  _inside_ a single file are run sequentially.

`dms-test` prefix matching changed to expect a `_` suffix as a delimiter.

---

docs: Add a note regarding output from running tests in parallel

test/helper/common.bash

@@ -9,16 +9,35 @@ __load_bats_helper
 
 # -------------------------------------------------------------------
 
+# like _run_in_container_explicit but infers ${1} by using the ENV CONTAINER_NAME
 function _run_in_container() {
   run docker exec "${CONTAINER_NAME}" "${@}"
 }
 
+# @param ${1} container name [REQUIRED]
+# @param ... command to execute
+function _run_in_container_explicit() {
+  local CONTAINER_NAME=${1:?Container name must be given when using explicit}
+  shift 1
+  run docker exec "${CONTAINER_NAME}" "${@}"
+}
+
 function _default_teardown() {
   docker rm -f "${CONTAINER_NAME}"
 }
 
 # -------------------------------------------------------------------
 
+# @param ${1} program name [REQUIRED]
+# @param ${2} container name [IF UNSET: ${CONTAINER_NAME}]
+function _check_if_process_is_running() {
+  local PROGRAM_NAME=${1:?Program name must be provided explicitly}
+  local CONTAINER_NAME=${2:-${CONTAINER_NAME}}
+  _run_in_container_explicit "${CONTAINER_NAME}" pgrep "${PROGRAM_NAME}"
+}
+
+# -------------------------------------------------------------------
+
 # @param ${1} timeout
 # @param --fatal-test <command eval string> additional test whose failure aborts immediately
 # @param ... test to run