Update opts.MemBytes to disable default, and move docker run/create/build to use opts.MemBytes

This fix made several updates:
1. Update opts.MemBytes so that default value will not show up.
   The reason is that in case a default value is decided by daemon,
   instead of client, we actually want to not show default value.
2. Move `docker run/create/build` to use opts.MemBytes for `--shm-size`
   This is to bring consistency between daemon and docker run
3. docs updates.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
Upstream-commit: 629abab4c0
Component: cli

components/cli/opts/opts.go

@@ -409,7 +409,13 @@ type MemBytes int64
 
 // String returns the string format of the human readable memory bytes
 func (m *MemBytes) String() string {
-	return units.BytesSize(float64(m.Value()))
+	// NOTE: In spf13/pflag/flag.go, "0" is considered as "zero value" while "0 B" is not.
+	// We return "0" in case value is 0 here so that the default value is hidden.
+	// (Sometimes "default 0 B" is actually misleading)
+	if m.Value() != 0 {
+		return units.BytesSize(float64(m.Value()))
+	}
+	return "0"
 }
 
 // Set sets the value of the MemBytes by passing a string