Re-init variables and trigger other init actions on RAT change

In order to not change the functionality due to phone refactor,
some variables should be reset to initial values on RAT change
otherwise stale values may be used.
Earlier some registrations were done (like for radio state) in
Phone constructors for which a response was expected right away.
Since that does not happen with the refactor, this CL also
includes changes to proactively query radio state.

Bug: 25793157
Change-Id: I33d1d5ea003c5abb69aad291f1903864c8a8f116