test: refactor test framework to use a rootfs skeleton

Instead of having to create files, and copying them in place for each
test, we move all static test files to a skeleton rootfs.  This makes
it a lot easier to get an overview of how things and how they work.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

test/skel/sbin/service.sh

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+cleanup()
+{
+	echo "Got signal, stopping ..."
+	rm -f /run/service.pid
+	exit 0
+}
+
+# Hook SIGUSR1 and dump trace to file system
+# shellcheck disable=SC2172
+trap 'echo USR1 > /tmp/usr1.log' USR1
+trap cleanup INT
+trap cleanup TERM
+trap cleanup QUIT
+trap cleanup EXIT
+
+echo $$ > /run/service.pid
+
+# sleep may exit on known signal, so
+# we cannot use 'set -e'
+while true; do
+	sleep 1
+done