add unit test for pkg/flags/Uint32FromFlag in uint32_test.go
add unit test for pkg/flags/Uint32FromFlag in uint32_test.go

Signed-off-by: Benjamin Wang <a1713d12b1b05630690f22cadfd282d625d8acb2@vmware.com>

etcd-io/etcd,mqliang/etcd,ajityagaty/etcd,etcd-io/etcd,mqliang/etcd,etcd-io/etcd,ajityagaty/etcd,mqliang/etcd,ajityagaty/etcd