Bug #2424: Fix nic-detach failure action
(cherry picked from commit c68571ecab8948536a857ff02e381d2a1a155c93)
Bug #2290: Fix typo

(cherry picked from commit f77ec81fb87bdd79f42d30f5aacdc9419acddb9c)
Bug #2467: live migration in xen4

(cherry picked from commit 563168e1ebe37812951e3a33bb77f4eaf644970e)
Bug #2467: add multiline_exec_and_log function to scripts_common.sh

(manually extracted from commit 514ffed512dd3602b4ff5f61eb395c45df6a4cfe)