OpenNebula: Add USER_RESTRICTED_ATTR feature
|Category:||Core & System|
Need to have possibility for refuse user to change some variables of his account.
USER_RESTRICTED_ATTR = "ALLOW_SCRATCH_ARMPITS"
Will refuse to override ALLOW_SCRATCH_ARMPITS variable.
This completely same like VM_RESTRICTED_ATTR, IMAGE_RESTRICTED_ATTR and VNET_RESTRICTED_ATTR, but applicable to users.