engine: copy vm/template permissions fixes

Changes:
- set the copyVmPermissions on all required places on FE
- the new permission is not assigned to the user creating the vm/template but
  to the user it has been assigned before
- made sure that the same permission is not added twice (to not violate the
  unique constraint on the permissions table

Change-Id: Ibe9d1b305c1275f695b954d52b8f49f4f775f119
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>