NSX: remove req_timeout as it's not longer used

This patch removes req_timeout from devstack as it's no longer used.
This was removed from neutron here:
    Id7244cd4d9316931f4f7df1c3b41b3a894f2909a

Change-Id: Ife901479605323e32f24e11266a232fddbd6bdca
Merge "NSX: remove req_timeout as it's not longer used"