Guard a debug output line

A line in the script writes out all interpolated variables into a text
file. It creates a large file, filling up the disk and slowing down the
tool. This commit guards the line with the debug option. No functional
changes.

src/Utility/OneWayNestScripts/interpolate_variables8.f90

@@ -443,7 +443,7 @@ program interpolate
         count_2d(1)=np; count_2d(2)=1
         iret=nf90_get_var(ncid4,itmp,eta2,start_2d,count_2d)
         if(iret/=NoErr) stop 'Failed to fetch elev'
-        write(98,*)it1,eta2
+        if(idebug==1) write(98,*)it1,eta2
 
         if(ifile>1) then !get 3D vars
           do ii=1,n_vars