Set journal_mode to truncate for SQLite in tests

no issue

- we would regularly see IO errors coming from SQLite, which caused
  random regression tests to fail
- the default journal_mode is `delete`, but this is slow and can cause
  issues when multiple tests try to remove the journal file
- `truncate` is faster and shouldn't cause these issues

core/test/utils/index.js

@@ -931,6 +931,13 @@ startGhost = function startGhost(options) {
             settingsCache.reset();
             return knexMigrator.init();
         })
+        .then(function setPragma() {
+            if (config.get('database:client') === 'sqlite3') {
+                return db.knex.raw('PRAGMA journal_mode = TRUNCATE;');
+            } else {
+                return Promise.resolve();
+            }
+        })
         .then(function initializeGhost() {
             urlService.resetGenerators();