Contrib content: create a further category for scripts

Not all contrib content is created equal, so let's just move scripts
to a properly named directory, in anticipation for different types of
content.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

selftests/checkall

@@ -19,6 +19,6 @@ if [ -z "$AVOCADO_SELF_CHECK" ]; then
     run_rc selftests/run
 else
     run_rc 'python setup.py develop --user'
-    run_rc 'scripts/avocado run `./contrib/avocado-find-unittests selftests/{unit,functional,doc}/*.py | xargs` --external-runner="/usr/bin/python -m unittest"'
+    run_rc 'scripts/avocado run `./contrib/scripts/avocado-find-unittests selftests/{unit,functional,doc}/*.py | xargs` --external-runner="/usr/bin/python -m unittest"'
 fi
 exit ${GR}