Switch to using tmt testing instead of STI

plans/build-iso.fmf

@@ -0,0 +1,7 @@
+summary: Run Lorax tests (build an iso, run mkksiso on it)
+prepare:
+    how: install
+    package:
+    - lorax
+execute:
+    script: ./tests/scripts/run_tests.sh

tests/provision.fmf

@@ -1,5 +0,0 @@
----
-
-standard-inventory-qcow2:
-  qemu:
-    m: 4G

tests/tests.yml

@@ -1,15 +0,0 @@
----
-# Run lorax with the new templates
-- hosts: localhost
-  roles:
-    - role: standard-test-basic
-      tags:
-        - classic
-
-      required_packages:
-        - lorax
-
-      tests:
-        - simple:
-            dir: scripts
-            run: ./run_tests.sh