Replace the redundant code with the utility function
Replace the redundant code with the utility function

Use the PositiveNotNullInt method to jugde the input in
gnocchi\rest\__init__.py

Change-Id: I167e8f1ff89219cbd1c884142eb8e83820e0b82d

gnocchixyz/gnocchi,gnocchixyz/gnocchi,sileht/gnocchi,leandroreox/gnocchi,sileht/gnocchi,leandroreox/gnocchi