Add read only command to get status of Finalization in OM & SCM.

Currently, the finalization client exposes only the "finalizeupgrade" command that starts finalization, and sees it to completion. In an already finalized cluster or a cluster where finalization is going on, the only way to get finalization status by another client is to run finalizeupgrade again (with --takeover flag if finalization is in progress). Since this is not very user intuitive, we can add a new admin command in OM and SCM to get finalization status of the component through a read only command, like

ozone admin om/scm finalization-status