Avoid plugin access while authorizing GET responses

Issue #16834

This patch removes the need for executing a plugin call while checking
authZ policies on returned data, since the plugin is going all the way
to NVP.
The database plugin will provide instead all the required info.

Change-Id: Ie2bd9174d7d7fd2f90f1ccaf25cd0895cd6808b2
NVP metadata access - create elevated context once

Issue #16833
Bug 1155051

This is a follow-up patch which fixes a problem with elevated
context not being passed to subroutines.

Change-Id: Ic270d8e48075b6b58117970ab870c3fb3962d93b
Fix netbindings for upgrade

Issue #16832

Change-Id: I70b238fb464f5584ee5f2ff32f4afabe3ab30b34
Merge "Fix netbindings for upgrade"
Merge "NVP metadata access - create elevated context once"
Merge "Avoid plugin access while authorizing GET responses"