In a case where we have only one action (that is having a info icon) should we still keep it in action overflow for Jelly Bean design or we can have it as an icon itself on the action bar? The reason being, the info is less often used so it can also goto action overflow. At the same time just for one action keeping stuffs in action overflow, kind of confused.
If you have only one action in the action overflow, then you really don't have an overflow as you can replace the action overflow with the action itself.
The only times I would recommend having an action overflow despite only having one action are:
In your case, it is clear that you don't want to discourage this action, and there is a clear, well known icon for the action. So I would recommend dropping the action overflow and having a single "Information" icon.
This is the perfect time to reference the Android "FIT scheme"
While "info" may not be used every time a user is in your activity, it is generally burdensome to tap the action overflow first then tap the info button. When there is a space constraint due to other actions, put it in the overflow. When info will not compete with more important actions (as in this case), put it on the action bar.
As a disclaimer, the FIT scheme is subjective and you know your application's use cases better than I.