Remove public default constructor from CMWeatherManager.RequestStatus [1/2]

RequestStatus holds only final constants and should not provide
public constructors. This class also should be final.

This patch also fix minor typos on RequestStatus javadoc

Change-Id: I0deb1d6a9b23eed83451dec352bb4c410e2378d6
TICKET: CYNGNOS-2441
(cherry picked from commit ad5e5d01)