NSX: bump http_timeout to 30 seconds

We've seen that sometimes NSX takes longer then 10 seconds to return
in production setups under high bursts. Setting this value to 30 seconds
seems more appropriate and solves the issue at load.

Suggestion by: Jacob Cherkas

Change-Id: If604d5d52d15cc1165e19d20b38774dfecec275f
Closes-bug: 1325055
Merge "NSX: bump http_timeout to 30 seconds"