2) Added new api - changeServiceForSystemVm - to support service offering upgrade for system vms
3) Removed global config parameters that are not in use anymore: consoleproxy.ram.size, consoleproxy.cpu.mhz, secstorage.vm.ram.size, secstorage.vm.cpu.mhz
Conflicts:
server/src/com/cloud/migration/Db20to21MigrationUtil.java