Run tests Docker in Docker (#261)

* Try running tests in Docker

* Spawn new container for each test

* Store test artifacts outside of mount

* When requested, build up to date image in test script

* sudo is unneccessary in containerized test env

* Skip azure test

* Backdate fixture file in JSON database

* Pin versions for azure tools

* Mount temp volume for /var/lib/docker to prevent dangling ones created by VOLUME instruction

* Fail backdating tests with message

* Add some documentation on test setup

* Cache images

* Run compose stacks with shortened default timeout

test/util.sh

@@ -15,9 +15,31 @@ fail () {
   exit 1
 }
 
+skip () {
+  echo "[test:${current_test:-none}:skip] "$1""
+  exit 0
+}
+
 expect_running_containers () {
   if [ "$(docker ps -q | wc -l)" != "$1" ]; then
     fail "Expected $1 containers to be running, instead seen: "$(docker ps -a | wc -l)""
   fi
   pass "$1 containers running."
 }
+
+docker() {
+  case $1 in
+    compose)
+      shift
+      case $1 in
+        up)
+          shift
+          command docker compose up --timeout 3 "$@";;
+        *)
+          command docker compose "$@";;
+      esac
+      ;;
+    *)
+      command docker "$@";;
+  esac
+}