CLOUDSTACK-4538: set default value of cpu.overprovisioning.factor and mem.overprovisioning.factor to 1

On a fresh environment, some values in cloud.configuration table are persisted in com.cloud.server.ConfigurationServerImpl.persistDefaultValues()
A default value need to be set before com.cloud.upgrade.DatabaseUpgradeChecker
(cherry picked from commit 1a67750cb66cf74175e2776ba3f3ba76fde0d1bb)