Making a change to drush so that it doesn't drop any database tables when doing site installs.

git-svn-id: file:///tmp/wdn_thm_drupal/branches/drupal-7.x@136 20a16fea-79d4-4915-8869-1ea9d5ebf173

sites/all/modules/drush/commands/core/site_install.drush.inc

@@ -54,6 +54,8 @@ function drush_core_pre_site_install() {
 
   // Now we can bootstrap up to the specified site if not already there.
   drush_bootstrap(DRUSH_BOOTSTRAP_DRUPAL_SITE);
+  // Don't drop databases.  No idea why they wanted to do that.
+  return;
 
   // Drop and create DB if needed.
   // TODO: support db-su like sql sync.