Use write connection and transactions in SQL patches

Summary:
Patches often read from slaves (possibly stale data) and use that information to write on master.
It causes problems when applying more patches quickly after each other because data created in previous patch may not be replicated yet.

Test Plan:
  $ bin/storage upgrade

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4483

resources/sql/patches/migrate-maniphest-dependencies.php

@@ -1,7 +1,10 @@
 <?php
 
 echo "Migrating task dependencies to edges...\n";
-foreach (new LiskMigrationIterator(new ManiphestTask()) as $task) {
+$table = new ManiphestTask();
+$table->openTransaction();
+
+foreach (new LiskMigrationIterator($table) as $task) {
   $id = $task->getID();
   echo "Task {$id}: ";
 
@@ -23,4 +26,5 @@ foreach (new LiskMigrationIterator(new ManiphestTask()) as $task) {
   echo "OKAY\n";
 }
 
+$table->saveTransaction();
 echo "Done.\n";