Fix issue with level of dividing streamline (rdxzb) being overwritten and affecting stochastic physics in ugwp

[mdtoyNOAA]

Description

As part of ccpp-physics PR#22, the order in which subroutines "gwdps_run" and "drag_suite_run" were called by subroutine "unified_ugwp_run" was reversed. Subroutine "drag_suite_run" is called last, but the variable "RDXZB" (the level of the dividing streamline for blocking) is initialized, which zeros out the value that was calculated in "gwdps_run". RDXZB is needed outside of the unified_ugwp subroutine by stochastic physics. This caused stochastic physics runs to crash. The bug was not caught by regression testing.

The problem has been fixed by changing the declaration of "RDXZB" from "intent(out)" to "intent(inout)" in drag_suite.F90 and drag_suite.meta, and initializing it in drag_suite.F90 only when the GSL drag suite blocking is performed, i.e., when "do_gsl_drag_ls_bl" is equal to .true.

Steps to Reproduce

This problem doesn't occur when running a deterministic forecast. It only causes crashes when running stochastic physics.