NSX sync cache: add a flag to skip item deletion

This new flag will prevent updates on single resources, which
can happen asynchronously to the main synchronization thread,
from processing the 'changed' flag for items in the cache and
delete items not present anymore in NSX.

This will avoid failures seen in CI runs where the sync
thread failed because of a KeyError because some items where
concurrently removed from the NSX cache.

Change-Id: I6a11b8dabb1e9481dc807b5fbba17c9027dad5f2
Closes-Bug: #1329650
NSX: return 400 if dscp set for trusted queue

If qos_marking is set to True, the code currently silently
drops the dscp setting and continues.

It is preferrable instead to notify the user of the invalid
setting returning a 400 error.

Change-Id: I7db1867712bd20f2030c56a42baac20e6ae76d0d
Closes-Bug: 1332062
Imported Translations from Transifex

Change-Id: I6d86131382188d4fa3537b235248b81d946be1c3
Merge "NSX: return 400 if dscp set for trusted queue"
Merge "NSX sync cache: add a flag to skip item deletion"