Fixed bug with setting OpenMP num threads

In Grib2Message.interpolate() method, fixed a bug where num_threads
was not being passed to the module-level function interpolate(),
which was setting the default value to 1.

Version bump to v2.2.1.

VERSION

@@ -1 +1 @@
-2.2.0
+2.2.1

src/grib2io/_grib2io.py

@@ -1312,7 +1312,7 @@ def interpolate(self, method, grid_def_out, method_options=None, drtn=None,
         elif msg.typeOfValues == 1:
             dtype = 'int32'
         msg._data = interpolate(self.data,method,Grib2GridDef.from_section3(self.section3),grid_def_out,
-                                method_options=method_options).reshape(msg.ny,msg.nx)
+                                method_options=method_options,num_threads=num_threads).reshape(msg.ny,msg.nx)
         msg.section5[0] = grid_def_out.npoints
         return msg